diff --git a/browser/components/privatebrowsing/test/browser/Makefile.in b/browser/components/privatebrowsing/test/browser/Makefile.in
index bdc591d3227..02377ab8ddc 100644
--- a/browser/components/privatebrowsing/test/browser/Makefile.in
+++ b/browser/components/privatebrowsing/test/browser/Makefile.in
@@ -20,10 +20,6 @@ MOCHITEST_BROWSER_FILES =  \
 		browser_privatebrowsing_concurrent.js \
 		browser_privatebrowsing_concurrent_page.html \
 		browser_privatebrowsing_crh.js \
-		browser_privatebrowsing_downloadLastDir.js \
-		browser_privatebrowsing_downloadLastDir_c.js \
-		browser_privatebrowsing_downloadLastDir_toggle.js \
-		browser_privatebrowsing_DownloadLastDirWithCPS.js \
 		browser_privatebrowsing_fastswitch.js \
 		browser_privatebrowsing_findbar.js \
 		browser_privatebrowsing_forgetthissite.js \
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_DownloadLastDirWithCPS.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_DownloadLastDirWithCPS.js
deleted file mode 100644
index 029b427e5e0..00000000000
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_DownloadLastDirWithCPS.js
+++ /dev/null
@@ -1,222 +0,0 @@
-/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-let downloadModule = {};
-Cu.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/FileUtils.jsm");
-
-let gDownloadLastDir = new downloadModule.DownloadLastDir(window);
-let pb = Cc["@mozilla.org/privatebrowsing;1"].
-         getService(Ci.nsIPrivateBrowsingService);
-
-function test() {
-  function clearHistory() {
-    // simulate clearing the private data
-    Services.obs.notifyObservers(null, "browser:purge-session-history", "");
-  }
-
-  is(typeof gDownloadLastDir, "object", "gDownloadLastDir should be a valid object");
-  is(gDownloadLastDir.file, null, "LastDir pref should be null to start with");
-
-  let tmpDir = FileUtils.getDir("TmpD", [], true);
-
-  let uri1 = Services.io.newURI("http://test1.com/", null, null);
-  let uri2 = Services.io.newURI("http://test2.com/", null, null);
-  let uri3 = Services.io.newURI("http://test3.com/", null, null);
-  let uri4 = Services.io.newURI("http://test4.com/", null, null);
-
-  function newDir() {
-    let dir = tmpDir.clone();
-    dir.append("testdir");
-    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
-    return dir;
-  }
-
-  let dir1 = newDir();
-  let dir2 = newDir();
-  let dir3 = newDir();
-  try {
-    { // set up last dir
-      gDownloadLastDir.setFile(null, tmpDir);
-      is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to the tmpDir");
-      isnot(gDownloadLastDir.file, tmpDir, "gDownloadLastDir.file should not be pointing to tmpDir");
-    }
-
-    { // set uri1 to dir1, all should now return dir1
-      // also check that a new object is returned
-      gDownloadLastDir.setFile(uri1, dir1);
-      is(gDownloadLastDir.file.path, dir1.path, "gDownloadLastDir should return dir1");
-      isnot(gDownloadLastDir.file, dir1, "gDownloadLastDir.file should not return dir1");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1"); // set in CPS
-      isnot(gDownloadLastDir.getFile(uri1), dir1, "getFile on uri1 should not return dir1");
-      is(gDownloadLastDir.getFile(uri2).path, dir1.path, "uri2 should return dir1"); // fallback
-      isnot(gDownloadLastDir.getFile(uri2), dir1, "getFile on uri2 should not return dir1");
-      is(gDownloadLastDir.getFile(uri3).path, dir1.path, "uri3 should return dir1"); // fallback
-      isnot(gDownloadLastDir.getFile(uri3), dir1, "getFile on uri3 should not return dir1");
-      is(gDownloadLastDir.getFile(uri4).path, dir1.path, "uri4 should return dir1"); // fallback
-      isnot(gDownloadLastDir.getFile(uri4), dir1, "getFile on uri4 should not return dir1");
-    }
-
-    { // set uri2 to dir2, all except uri1 should now return dir2
-      gDownloadLastDir.setFile(uri2, dir2);
-      is(gDownloadLastDir.file.path, dir2.path, "gDownloadLastDir should point to dir2");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1"); // set in CPS
-      is(gDownloadLastDir.getFile(uri2).path, dir2.path, "uri2 should return dir2"); // set in CPS
-      is(gDownloadLastDir.getFile(uri3).path, dir2.path, "uri3 should return dir2"); // fallback
-      is(gDownloadLastDir.getFile(uri4).path, dir2.path, "uri4 should return dir2"); // fallback
-    }
-
-    { // set uri3 to dir3, all except uri1 and uri2 should now return dir3
-      gDownloadLastDir.setFile(uri3, dir3);
-      is(gDownloadLastDir.file.path, dir3.path, "gDownloadLastDir should point to dir3");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1"); // set in CPS
-      is(gDownloadLastDir.getFile(uri2).path, dir2.path, "uri2 should return dir2"); // set in CPS
-      is(gDownloadLastDir.getFile(uri3).path, dir3.path, "uri3 should return dir3"); // set in CPS
-      is(gDownloadLastDir.getFile(uri4).path, dir3.path, "uri4 should return dir4"); // fallback
-    }
-
-    { // set uri1 to dir2, all except uri3 should now return dir2
-      gDownloadLastDir.setFile(uri1, dir2);
-      is(gDownloadLastDir.file.path, dir2.path, "gDownloadLastDir should point to dir2");
-      is(gDownloadLastDir.getFile(uri1).path, dir2.path, "uri1 should return dir2"); // set in CPS
-      is(gDownloadLastDir.getFile(uri2).path, dir2.path, "uri2 should return dir2"); // set in CPS
-      is(gDownloadLastDir.getFile(uri3).path, dir3.path, "uri3 should return dir3"); // set in CPS
-      is(gDownloadLastDir.getFile(uri4).path, dir2.path, "uri4 should return dir2"); // fallback
-    }
-
-    { // check clearHistory removes all data
-      clearHistory();
-      is(gDownloadLastDir.file, null, "clearHistory removes all data");
-      is(Services.contentPrefs.hasPref(uri1, "browser.download.lastDir"), false, "LastDir preference should be absent");
-      is(gDownloadLastDir.getFile(uri1), null, "uri1 should point to null");
-      is(gDownloadLastDir.getFile(uri2), null, "uri2 should point to null");
-      is(gDownloadLastDir.getFile(uri3), null, "uri3 should point to null");
-      is(gDownloadLastDir.getFile(uri4), null, "uri4 should point to null");
-    }
-
-    Services.prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
-
-    { // check data set outside PB mode is remembered
-      gDownloadLastDir.setFile(null, tmpDir);
-      pb.privateBrowsingEnabled = true;
-      is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to tmpDir inside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, tmpDir.path, "uri1 should return tmpDir inside PB mode");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to tmpDir outside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, tmpDir.path, "uri1 should return tmpDir outside PB mode");
-
-      clearHistory();
-    }
-
-    { // check data set using CPS outside PB mode is remembered
-      gDownloadLastDir.setFile(uri1, dir1);
-      pb.privateBrowsingEnabled = true;
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should point to dir1 inside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1 inside PB mode");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should point to dir1 outside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1 outside PB mode");
-
-      clearHistory();
-    }
-
-    { // check data set inside PB mode is forgotten
-      pb.privateBrowsingEnabled = true;
-      gDownloadLastDir.setFile(null, tmpDir);
-      is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should return tmpDir inside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, tmpDir.path, "uri1 should return tmpDir inside PB mode");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file, null, "LastDir should be null outside PB mode");
-      is(gDownloadLastDir.getFile(uri1), null, "uri1 should return null outside PB mode");
-
-      clearHistory();
-    }
-
-    { // check data set using CPS inside PB mode is forgotten
-      pb.privateBrowsingEnabled = true;
-      gDownloadLastDir.setFile(uri1, dir1);
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should point to dir1 inside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1 inside PB mode");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file, null, "LastDir should point to null outside PB mode");
-      is(gDownloadLastDir.getFile(uri1), null, "uri1 should return null outside PB mode");
-
-      clearHistory();
-    }
-
-    { // check data set outside PB mode but changed inside is remembered correctly
-      gDownloadLastDir.setFile(uri1, dir1);
-      pb.privateBrowsingEnabled = true;
-      gDownloadLastDir.setFile(uri1, dir2);
-      is(gDownloadLastDir.file.path, dir2.path, "LastDir should point to dir2 inside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, dir2.path, "uri1 should return dir2 inside PB mode");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should point to dir1 outside PB mode");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1 outside PB mode");
-
-      // check that the last dir store got cleared
-      pb.privateBrowsingEnabled = true;
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should be cleared");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1");
-
-      pb.privateBrowsingEnabled = false;
-      clearHistory();
-    }
-
-    { // check clearHistory inside PB mode clears data outside PB mode
-      pb.privateBrowsingEnabled = true;
-      gDownloadLastDir.setFile(uri1, dir2);
-
-      clearHistory();
-      is(gDownloadLastDir.file, null, "LastDir should be null afer clearing history");
-      is(gDownloadLastDir.getFile(uri1), null, "uri1 should return null");
-
-      pb.privateBrowsingEnabled = false;
-      is(gDownloadLastDir.file, null, "LastDir should be null");
-      is(gDownloadLastDir.getFile(uri1), null, "uri1 should return null");
-    }
-
-    { // check that disabling CPS works
-      Services.prefs.setBoolPref("browser.download.lastDir.savePerSite", false);
-
-      gDownloadLastDir.setFile(uri1, dir1);
-      is(gDownloadLastDir.file.path, dir1.path, "LastDir should be set to dir1");
-      is(gDownloadLastDir.getFile(uri1).path, dir1.path, "uri1 should return dir1");
-      is(gDownloadLastDir.getFile(uri2).path, dir1.path, "uri2 should return dir1");
-      is(gDownloadLastDir.getFile(uri3).path, dir1.path, "uri3 should return dir1");
-      is(gDownloadLastDir.getFile(uri4).path, dir1.path, "uri4 should return dir1");
-
-      gDownloadLastDir.setFile(uri2, dir2);
-      is(gDownloadLastDir.file.path, dir2.path, "LastDir should be set to dir2");
-      is(gDownloadLastDir.getFile(uri1).path, dir2.path, "uri1 should return dir2");
-      is(gDownloadLastDir.getFile(uri2).path, dir2.path, "uri2 should return dir2");
-      is(gDownloadLastDir.getFile(uri3).path, dir2.path, "uri3 should return dir2");
-      is(gDownloadLastDir.getFile(uri4).path, dir2.path, "uri4 should return dir2");
-
-      Services.prefs.clearUserPref("browser.download.lastDir.savePerSite");
-    }
-
-    { // check that passing null to setFile clears the stored value
-      gDownloadLastDir.setFile(uri3, dir3);
-      is(gDownloadLastDir.getFile(uri3).path, dir3.path, "LastDir should be set to dir3");
-      gDownloadLastDir.setFile(uri3, null);
-      is(gDownloadLastDir.getFile(uri3), null, "uri3 should return null");
-    }
-  } finally {
-      dir1.remove(true);
-      dir2.remove(true);
-      dir3.remove(true);
-      Services.prefs.clearUserPref("browser.download.lastDir.savePerSite");
-      Services.prefs.clearUserPref("browser.download.lastDir");
-      gDownloadLastDir.cleanupPrivateFile();
-      delete FileUtils;
-  }
-}
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir.js
deleted file mode 100644
index 3a00f673f3b..00000000000
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir.js
+++ /dev/null
@@ -1,98 +0,0 @@
-/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-let downloadModule = {};
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/XPCOMUtils.jsm");
-Cu.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
-Cu.import("resource://gre/modules/FileUtils.jsm");
-Cu.import("resource://mochikit/MockFilePicker.jsm");
-
-let launcher = {
-  source: Services.io.newURI("http://test1.com/file", null, null)
-};
-let pb = Cc["@mozilla.org/privatebrowsing;1"].
-         getService(Ci.nsIPrivateBrowsingService);
-let gDownloadLastDir = new downloadModule.DownloadLastDir(window);
-
-MockFilePicker.init();
-MockFilePicker.returnValue = Ci.nsIFilePicker.returnOK;
-
-function test() {
-  Services.prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
-  let prefs = Services.prefs.getBranch("browser.download.");
-  let launcherDialog = Cc["@mozilla.org/helperapplauncherdialog;1"].
-                       getService(Ci.nsIHelperAppLauncherDialog);
-  let tmpDir = FileUtils.getDir("TmpD", [], true);
-  function newDirectory() {
-    let dir = tmpDir.clone();
-    dir.append("testdir");
-    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
-    return dir;
-  }
-  function newFileInDirectory(dir) {
-    let file = dir.clone();
-    file.append("testfile");
-    file.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0600);
-    return file;
-  }
-
-  let dir1 = newDirectory();
-  let dir2 = newDirectory();
-  let dir3 = newDirectory();
-  let file1 = newFileInDirectory(dir1);
-  let file2 = newFileInDirectory(dir2);
-  let file3 = newFileInDirectory(dir3);
-
-  // cleanup functions registration
-  registerCleanupFunction(function () {
-    Services.prefs.clearUserPref("browser.privatebrowsing.keep_current_session");
-    Services.prefs.clearUserPref("browser.download.lastDir");
-    [dir1, dir2, dir3].forEach(function(dir) dir.remove(true));
-    MockFilePicker.cleanup();
-    gDownloadLastDir.cleanupPrivateFile();
-    delete FileUtils;
-  });
-
-  let context = gBrowser.selectedBrowser.contentWindow;
-
-  prefs.setComplexValue("lastDir", Ci.nsIFile, tmpDir);
-  MockFilePicker.returnFiles = [file1];
-  let file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
-  ok(!!file, "promptForSaveToFile correctly returned a file");
-  // file picker should start with browser.download.lastDir
-  is(MockFilePicker.displayDirectory.path, tmpDir.path, "File picker should start with browser.download.lastDir");
-  // browser.download.lastDir should be modified before entering the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should be modified before entering the PB mode");
-  // gDownloadLastDir should be usable outside of the private browsing mode
-  is(gDownloadLastDir.file.path, dir1.path, "gDownloadLastDir should be usable outside of the PB mode");
-
-  pb.privateBrowsingEnabled = true;
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should be that set before entering PB mode");
-  MockFilePicker.returnFiles = [file2];
-  MockFilePicker.displayDirectory = null;
-  file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
-  ok(!!file, "promptForSaveToFile correctly returned a file");
-  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
-  is(MockFilePicker.displayDirectory.path, dir1.path, "Start with LastDir as set before entering the PB mode");
-  // browser.download.lastDir should not be modified inside the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should not be modified inside the PB mode");
-  // but gDownloadLastDir should be modified
-  is(gDownloadLastDir.file.path, dir2.path, "gDownloadLastDir should be modified inside PB mode");
-
-  pb.privateBrowsingEnabled = false;
-  // gDownloadLastDir should be cleared after leaving the private browsing mode
-  is(gDownloadLastDir.file.path, dir1.path, "gDownloadLastDir should be cleared after leaving the PB mode");
-  MockFilePicker.returnFiles = [file3];
-  MockFilePicker.displayDirectory = null;
-  file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
-  ok(!!file, "promptForSaveToFile correctly returned a file");
-  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
-  is(MockFilePicker.displayDirectory.path, dir1.path, "Start with LastDir as set before entering the PB mode");
-  // browser.download.lastDir should be modified after leaving the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir3.path, "LastDir should be modified after leaving the PB mode");
-  // gDownloadLastDir should be usable after leaving the private browsing mode
-  is(gDownloadLastDir.file.path, dir3.path, "gDownloadLastDir should be usable after leaving the PB mode");
-}
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_c.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_c.js
deleted file mode 100644
index 976b4801e3e..00000000000
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_c.js
+++ /dev/null
@@ -1,112 +0,0 @@
-/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-let downloadModule = {};
-Cu.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
-Cu.import("resource://gre/modules/FileUtils.jsm");
-Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://mochikit/MockFilePicker.jsm");
-
-let pb = Cc["@mozilla.org/privatebrowsing;1"].
-         getService(Ci.nsIPrivateBrowsingService);
-let gDownloadLastDir = new downloadModule.DownloadLastDir(window);
-
-MockFilePicker.init();
-MockFilePicker.returnValue = Ci.nsIFilePicker.returnOK;
-
-function test() {
-  let stringBundleToRestore = ContentAreaUtils.stringBundle;
-  let validateFileNameToRestore = validateFileName;
-
-  Services.prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
-  let prefs = Services.prefs.getBranch("browser.download.");
-  let tmpDir = FileUtils.getDir("TmpD", [], true);
-  function newDirectory() {
-    let dir = tmpDir.clone();
-    dir.append("testdir");
-    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
-    return dir;
-  }
-
-  function newFileInDirectory(dir) {
-    let file = dir.clone();
-    file.append("testfile");
-    file.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0600);
-    return file;
-  }
-
-  let dir1 = newDirectory();
-  let dir2 = newDirectory();
-  let dir3 = newDirectory();
-  let file1 = newFileInDirectory(dir1);
-  let file2 = newFileInDirectory(dir2);
-  let file3 = newFileInDirectory(dir3);
-
-  // cleanup function registration
-  registerCleanupFunction(function () {
-    Services.prefs.clearUserPref("browser.privatebrowsing.keep_current_session");
-    Services.prefs.clearUserPref("browser.download.lastDir");
-    [dir1, dir2, dir3].forEach(function(dir) dir.remove(true));
-    MockFilePicker.cleanup();
-    ContentAreaUtils.stringBundle = stringBundleToRestore;
-    validateFileName = validateFileNameToRestore;
-    gDownloadLastDir.cleanupPrivateFile();
-    delete FileUtils;
-  });
-
-  // Overwrite stringBundle to return an object masquerading as a string bundle
-  delete ContentAreaUtils.stringBundle;
-  ContentAreaUtils.stringBundle = {
-    GetStringFromName: function() ""
-  };
-
-  // Overwrite validateFileName to validate everything
-  validateFileName = function(foo) foo;
-
-  let params = {
-    fpTitleKey: "test",
-    fileInfo: new FileInfo("test.txt", "test.txt", "test", "txt", "http://mozilla.org/test.txt"),
-    contentType: "text/plain",
-    saveMode: SAVEMODE_FILEONLY,
-    saveAsType: kSaveAsType_Complete,
-    file: null
-  };
-
-  prefs.setComplexValue("lastDir", Ci.nsIFile, tmpDir);
-  MockFilePicker.returnFiles = [file1];
-  MockFilePicker.displayDirectory = null;
-  ok(getTargetFile(params), "Show the file picker dialog with given params");
-  // file picker should start with browser.download.lastDir
-  is(MockFilePicker.displayDirectory.path, tmpDir.path, "file picker should start with browser.download.lastDir");
-  // browser.download.lastDir should be modified before entering the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should be modified before entering PB mode");
-  // gDownloadLastDir should be usable outside of the private browsing mode
-  is(gDownloadLastDir.file.path, dir1.path, "gDownloadLastDir should be usable outside of the PB mode");
-
-  pb.privateBrowsingEnabled = true;
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should be that set before PB mode");
-  MockFilePicker.returnFiles = [file2];
-  MockFilePicker.displayDirectory = null;
-  ok(getTargetFile(params), "Show the file picker dialog with the given params");
-  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
-  is(MockFilePicker.displayDirectory.path, dir1.path, "File picker should start with LastDir set before entering PB mode");
-  // browser.download.lastDir should not be modified inside the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir1.path, "LastDir should not be modified inside PB mode");
-  // but gDownloadLastDir should be modified
-  is(gDownloadLastDir.file.path, dir2.path, "gDownloadLastDir should be modified");
-
-  pb.privateBrowsingEnabled = false;
-  // gDownloadLastDir should be cleared after leaving the private browsing mode
-  is(gDownloadLastDir.file.path, dir1.path, "gDownloadLastDir should be cleared after leaving PB mode");
-  MockFilePicker.returnFiles = [file3];
-  MockFilePicker.displayDirectory = null;
-  ok(getTargetFile(params), "Show the file picker dialog with the given params");
-  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
-  is(MockFilePicker.displayDirectory.path, dir1.path, "File picker should start with LastDir set before PB mode");
-  // browser.download.lastDir should be modified after leaving the private browsing mode
-  is(prefs.getComplexValue("lastDir", Ci.nsIFile).path, dir3.path, "LastDir should be modified after leaving PB mode");
-  // gDownloadLastDir should be usable after leaving the private browsing mode
-  is(gDownloadLastDir.file.path, dir3.path, "gDownloadLastDir should be usable after leaving PB mode");
-}
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_toggle.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_toggle.js
deleted file mode 100644
index bd1148c6310..00000000000
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_downloadLastDir_toggle.js
+++ /dev/null
@@ -1,74 +0,0 @@
-/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-let downloadModule = {};
-Cu.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
-Cu.import("resource://gre/modules/FileUtils.jsm");
-Cu.import("resource://gre/modules/Services.jsm");
-
-let gDownloadLastDir = new downloadModule.DownloadLastDir(window);
-let pb = Cc["@mozilla.org/privatebrowsing;1"].
-         getService(Ci.nsIPrivateBrowsingService);
-
-function test() {
-  function clearHistory() {
-    // simulate clearing the private data
-    Services.obs.notifyObservers(null, "browser:purge-session-history", "");
-  }
-
-  is(typeof gDownloadLastDir, "object", "gDownloadLastDir should be a valid object");
-  is(gDownloadLastDir.file, null, "gDownloadLastDir.file should be null to start with");
-  let tmpDir = FileUtils.getDir("TmpD", [], true);
-  let newDir = tmpDir.clone();
-
-  registerCleanupFunction(function () {
-    Services.prefs.clearUserPref("browser.privatebrowsing.keep_current_session");
-    Services.prefs.clearUserPref("browser.download.lastDir");
-    newDir.remove(true);
-    gDownloadLastDir.cleanupPrivateFile();
-    delete FileUtils;
-  });
-
-  newDir.append("testdir");
-  newDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
-
-  gDownloadLastDir.file = tmpDir;
-  is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to the temporary directory");
-  isnot(gDownloadLastDir.file, tmpDir, "gDownloadLastDir.file should not be pointing to the tmpDir");
-
-  gDownloadLastDir.file = 1; // not an nsIFile
-  is(gDownloadLastDir.file, null, "gDownloadLastDir.file should be null");
-  gDownloadLastDir.file = tmpDir;
-
-  clearHistory();
-  is(gDownloadLastDir.file, null, "gDownloadLastDir.file should be null");
-  gDownloadLastDir.file = tmpDir;
-
-  Services.prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
-
-  pb.privateBrowsingEnabled = true;
-  is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to the temporary directory");
-  isnot(gDownloadLastDir.file, tmpDir, "gDownloadLastDir.file should not be pointing to the tmpDir");
-
-  pb.privateBrowsingEnabled = false;
-  is(gDownloadLastDir.file.path, tmpDir.path, "LastDir should point to the tmpDir");
-  pb.privateBrowsingEnabled = true;
-
-  gDownloadLastDir.file = newDir;
-  is(gDownloadLastDir.file.path, newDir.path, "gDownloadLastDir should be modified in PB mode");
-  isnot(gDownloadLastDir.file, newDir, "gDownloadLastDir should not point to the newDir");
-
-  pb.privateBrowsingEnabled = false;
-  is(gDownloadLastDir.file.path, tmpDir.path, "gDownloadLastDir should point to the earlier directory outside PB mode");
-  isnot(gDownloadLastDir.file, tmpDir, "gDownloadLastDir should not be modifief outside PB mode");
-
-  pb.privateBrowsingEnabled = true;
-  isnot(gDownloadLastDir.file, null, "gDownloadLastDir should not be null inside PB mode");
-  clearHistory();
-  is(gDownloadLastDir.file, null, "gDownloadLastDir should be null after clearing history");
-
-  pb.privateBrowsingEnabled = false;
-  is(gDownloadLastDir.file, null, "gDownloadLastDir should be null outside PB mode");
-}
diff --git a/toolkit/content/contentAreaUtils.js b/toolkit/content/contentAreaUtils.js
index 4489954161c..1fb00c90f0b 100644
--- a/toolkit/content/contentAreaUtils.js
+++ b/toolkit/content/contentAreaUtils.js
@@ -1,4 +1,4 @@
-# -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- 
+# -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -431,7 +431,7 @@ function internalPersist(persistArgs)
  * Structure for holding info about automatically supplied parameters for
  * internalSave(...). This allows parameters to be supplied so the user does not
  * need to be prompted for file info.
- * @param aFileAutoChosen This is an nsIFile object that has been
+ * @param aFileAutoChosen This is an nsILocalFile object that has been
  *        pre-determined as the filename for the target to save to
  * @param aUriAutoChosen  This is the nsIURI object for the target
  */
@@ -525,13 +525,13 @@ function initFileInfo(aFI, aURL, aURLCharset, aDocument,
  */
 function getTargetFile(aFpP, /* optional */ aSkipPrompt, /* optional */ aRelatedURI)
 {
-  let downloadModule = {};
-  Components.utils.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
-  var gDownloadLastDir = new downloadModule.DownloadLastDir(window);
+  if (!getTargetFile.gDownloadLastDir)
+    Components.utils.import("resource://gre/modules/DownloadLastDir.jsm", getTargetFile);
+  var gDownloadLastDir = getTargetFile.gDownloadLastDir;
 
   var prefs = getPrefsBrowserDownload("browser.download.");
   var useDownloadDir = prefs.getBoolPref("useDownloadDir");
-  const nsIFile = Components.interfaces.nsIFile;
+  const nsILocalFile = Components.interfaces.nsILocalFile;
 
   if (!aSkipPrompt)
     useDownloadDir = false;
@@ -568,7 +568,7 @@ function getTargetFile(aFpP, /* optional */ aSkipPrompt, /* optional */ aRelated
     // Default to desktop.
     var fileLocator = Components.classes["@mozilla.org/file/directory_service;1"]
                                 .getService(Components.interfaces.nsIProperties);
-    dir = fileLocator.get("Desk", nsIFile);
+    dir = fileLocator.get("Desk", nsILocalFile);
   }
 
   var fp = makeFilePicker();
@@ -600,11 +600,11 @@ function getTargetFile(aFpP, /* optional */ aSkipPrompt, /* optional */ aRelated
     prefs.setIntPref("save_converter_index", fp.filterIndex);
 
   // Do not store the last save directory as a pref inside the private browsing mode
-  var directory = fp.file.parent.QueryInterface(nsIFile);
+  var directory = fp.file.parent.QueryInterface(nsILocalFile);
   gDownloadLastDir.setFile(aRelatedURI, directory);
 
   fp.file.leafName = validateFileName(fp.file.leafName);
-
+  
   aFpP.saveAsType = fp.filterIndex;
   aFpP.file = fp.file;
   aFpP.fileURL = fp.fileURL;
diff --git a/toolkit/content/tests/unit/test_privatebrowsing_downloadLastDir_c.js b/toolkit/content/tests/unit/test_privatebrowsing_downloadLastDir_c.js
new file mode 100644
index 00000000000..56564130df8
--- /dev/null
+++ b/toolkit/content/tests/unit/test_privatebrowsing_downloadLastDir_c.js
@@ -0,0 +1,130 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Ci = Components.interfaces;
+const Cc = Components.classes;
+
+function loadUtilsScript() {
+  let loader = Cc["@mozilla.org/moz/jssubscript-loader;1"].
+               getService(Ci.mozIJSSubScriptLoader);
+  loader.loadSubScript("chrome://global/content/contentAreaUtils.js");
+  Components.utils.import("resource://gre/modules/DownloadLastDir.jsm");
+}
+
+do_get_profile();
+
+let window = {};
+function run_test()
+{
+  let pb;
+  try {
+    pb = Cc["@mozilla.org/privatebrowsing;1"].
+         getService(Ci.nsIPrivateBrowsingService);
+  } catch (e) {
+    print("PB service is not available, bail out");
+    return;
+  }
+
+  loadUtilsScript();
+
+  let prefsService = Cc["@mozilla.org/preferences-service;1"].
+                     getService(Ci.nsIPrefService).
+                     QueryInterface(Ci.nsIPrefBranch);
+  prefsService.setBoolPref("browser.privatebrowsing.keep_current_session", true);
+  let prefs = prefsService.getBranch("browser.download.");
+  let dirSvc = Cc["@mozilla.org/file/directory_service;1"].
+               getService(Ci.nsIProperties);
+  let tmpDir = dirSvc.get("TmpD", Ci.nsILocalFile);
+  function newDirectory() {
+    let dir = tmpDir.clone();
+    dir.append("testdir" + Math.floor(Math.random() * 10000));
+    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
+    return dir;
+  }
+  function newFileInDirectory(dir) {
+    let file = dir.clone();
+    file.append("testfile" + Math.floor(Math.random() * 10000));
+    file.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0600);
+    return file;
+  }
+  let dir1 = newDirectory();
+  let dir2 = newDirectory();
+  let dir3 = newDirectory();
+  let file1 = newFileInDirectory(dir1);
+  let file2 = newFileInDirectory(dir2);
+  let file3 = newFileInDirectory(dir3);
+
+  // overwrite makeFilePicker, as we don't want to create a real filepicker object
+  let fp = {
+    appendFilter: function() {},
+    appendFilters: function() {},
+    init: function() {},
+    show: function() Ci.nsIFilePicker.returnOK,
+    displayDirectory: null,
+    file: file1
+  };
+  makeFilePicker = function() fp;
+
+  // Overwrite stringBundle to return an object masquerading as a string bundle
+  delete ContentAreaUtils.stringBundle;
+  ContentAreaUtils.stringBundle = {
+    GetStringFromName: function() ""
+  };
+
+  // Overwrite validateFileName to validate everything
+  validateFileName = function(foo) foo;
+
+  let params = {
+    fpTitleKey: "test",
+    fileInfo: new FileInfo("test.txt", "test.txt", "test", "txt", "http://mozilla.org/test.txt"),
+    contentType: "text/plain",
+    saveMode: SAVEMODE_FILEONLY,
+    saveAsType: kSaveAsType_Complete,
+    file: null
+  };
+
+  prefs.setComplexValue("lastDir", Ci.nsILocalFile, tmpDir);
+
+  do_check_true(getTargetFile(params));
+  // file picker should start with browser.download.lastDir
+  do_check_eq(fp.displayDirectory.path, tmpDir.path);
+  // browser.download.lastDir should be modified before entering the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  // gDownloadLastDir should be usable outside of the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir1.path);
+
+  pb.privateBrowsingEnabled = true;
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  fp.file = file2;
+  fp.displayDirectory = null;
+  do_check_true(getTargetFile(params));
+  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
+  do_check_eq(fp.displayDirectory.path, dir1.path);
+  // browser.download.lastDir should not be modified inside the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  // but gDownloadLastDir should be modified
+  do_check_eq(gDownloadLastDir.file.path, dir2.path);
+
+  pb.privateBrowsingEnabled = false;
+  // gDownloadLastDir should be cleared after leaving the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir1.path);
+  fp.file = file3;
+  fp.displayDirectory = null;
+  do_check_true(getTargetFile(params));
+  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
+  do_check_eq(fp.displayDirectory.path, dir1.path);
+  // browser.download.lastDir should be modified after leaving the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir3.path);
+  // gDownloadLastDir should be usable after leaving the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir3.path);
+
+  // cleanup
+  Cc["@mozilla.org/observer-service;1"]
+    .getService(Ci.nsIObserverService)
+    .notifyObservers(null, "quit-application", null);
+
+  prefsService.clearUserPref("browser.privatebrowsing.keep_current_session");
+  [dir1, dir2, dir3].forEach(function(dir) dir.remove(true));
+}
diff --git a/toolkit/content/tests/unit/xpcshell.ini b/toolkit/content/tests/unit/xpcshell.ini
index eb32f5d3e07..6efc4cc46a6 100644
--- a/toolkit/content/tests/unit/xpcshell.ini
+++ b/toolkit/content/tests/unit/xpcshell.ini
@@ -4,4 +4,5 @@ tail =
 
 [test_contentAreaUtils.js]
 [test_dict.js]
+[test_privatebrowsing_downloadLastDir_c.js]
 [test_propertyListsUtils.js]
diff --git a/toolkit/mozapps/downloads/DownloadLastDir.jsm b/toolkit/mozapps/downloads/DownloadLastDir.jsm
index 72ccf1b1d68..ee97b97416c 100644
--- a/toolkit/mozapps/downloads/DownloadLastDir.jsm
+++ b/toolkit/mozapps/downloads/DownloadLastDir.jsm
@@ -1,4 +1,3 @@
-/* -*- Mode: javascript; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
@@ -26,12 +25,18 @@
 
 const LAST_DIR_PREF = "browser.download.lastDir";
 const SAVE_PER_SITE_PREF = LAST_DIR_PREF + ".savePerSite";
-const nsIFile = Components.interfaces.nsIFile;
+const PBSVC_CID = "@mozilla.org/privatebrowsing;1";
+const nsILocalFile = Components.interfaces.nsILocalFile;
 
-var EXPORTED_SYMBOLS = [ "DownloadLastDir" ];
+var EXPORTED_SYMBOLS = [ "gDownloadLastDir" ];
 
 Components.utils.import("resource://gre/modules/Services.jsm");
-Components.utils.import("resource://gre/modules/PrivateBrowsingUtils.jsm");
+
+let pbSvc = null;
+if (PBSVC_CID in Components.classes) {
+  pbSvc = Components.classes[PBSVC_CID]
+                    .getService(Components.interfaces.nsIPrivateBrowsingService);
+}
 
 let observer = {
   QueryInterface: function (aIID) {
@@ -43,8 +48,12 @@ let observer = {
   },
   observe: function (aSubject, aTopic, aData) {
     switch (aTopic) {
-      case "last-pb-context-exited":
-        gDownloadLastDirFile = null;
+      case "private-browsing":
+        if (aData == "enter")
+          gDownloadLastDirFile = readLastDirPref();
+        else if (aData == "exit") {
+          gDownloadLastDirFile = null;
+        }
         break;
       case "browser:purge-session-history":
         gDownloadLastDirFile = null;
@@ -58,12 +67,12 @@ let observer = {
 
 let os = Components.classes["@mozilla.org/observer-service;1"]
                    .getService(Components.interfaces.nsIObserverService);
-os.addObserver(observer, "last-pb-context-exited", true);
+os.addObserver(observer, "private-browsing", true);
 os.addObserver(observer, "browser:purge-session-history", true);
 
 function readLastDirPref() {
   try {
-    return Services.prefs.getComplexValue(LAST_DIR_PREF, nsIFile);
+    return Services.prefs.getComplexValue(LAST_DIR_PREF, nsILocalFile);
   }
   catch (e) {
     return null;
@@ -73,34 +82,23 @@ function readLastDirPref() {
 function isContentPrefEnabled() {
   try {
     return Services.prefs.getBoolPref(SAVE_PER_SITE_PREF);
-  }
+  } 
   catch (e) {
     return true;
   }
 }
 
 let gDownloadLastDirFile = readLastDirPref();
-
-function DownloadLastDir(aWindow) {
-  this.window = aWindow;
-}
-
-DownloadLastDir.prototype = {
-  isPrivate: function DownloadLastDir_isPrivate() {
-    return PrivateBrowsingUtils.isWindowPrivate(this.window);
-  },
+let gDownloadLastDir = {
   // compat shims
   get file() { return this.getFile(); },
   set file(val) { this.setFile(null, val); },
-  cleanupPrivateFile: function () {
-    gDownloadLastDirFile = null;
-  },
   getFile: function (aURI) {
     if (aURI && isContentPrefEnabled()) {
       let lastDir = Services.contentPrefs.getPref(aURI, LAST_DIR_PREF);
       if (lastDir) {
         var lastDirFile = Components.classes["@mozilla.org/file/local;1"]
-                                    .createInstance(Components.interfaces.nsIFile);
+                                    .createInstance(Components.interfaces.nsILocalFile);
         lastDirFile.initWithPath(lastDir);
         return lastDirFile;
       }
@@ -108,11 +106,8 @@ DownloadLastDir.prototype = {
     if (gDownloadLastDirFile && !gDownloadLastDirFile.exists())
       gDownloadLastDirFile = null;
 
-    if (this.isPrivate()) {
-      if (!gDownloadLastDirFile)
-        gDownloadLastDirFile = readLastDirPref();
+    if (pbSvc && pbSvc.privateBrowsingEnabled)
       return gDownloadLastDirFile;
-    }
     else
       return readLastDirPref();
   },
@@ -123,14 +118,14 @@ DownloadLastDir.prototype = {
       else
         Services.contentPrefs.removePref(aURI, LAST_DIR_PREF);
     }
-    if (this.isPrivate()) {
+    if (pbSvc && pbSvc.privateBrowsingEnabled) {
       if (aFile instanceof Components.interfaces.nsIFile)
         gDownloadLastDirFile = aFile.clone();
       else
         gDownloadLastDirFile = null;
     } else {
       if (aFile instanceof Components.interfaces.nsIFile)
-        Services.prefs.setComplexValue(LAST_DIR_PREF, nsIFile, aFile);
+        Services.prefs.setComplexValue(LAST_DIR_PREF, nsILocalFile, aFile);
       else if (Services.prefs.prefHasUserValue(LAST_DIR_PREF))
         Services.prefs.clearUserPref(LAST_DIR_PREF);
     }
diff --git a/toolkit/mozapps/downloads/nsHelperAppDlg.js b/toolkit/mozapps/downloads/nsHelperAppDlg.js
index c2699aef2bb..11436fcf89c 100644
--- a/toolkit/mozapps/downloads/nsHelperAppDlg.js
+++ b/toolkit/mozapps/downloads/nsHelperAppDlg.js
@@ -1,4 +1,4 @@
-/* -*- Mode: javascript; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=2 et sw=2 tw=80: */
 /*
 # This Source Code Form is subject to the terms of the Mozilla Public
@@ -97,9 +97,8 @@ nsUnknownContentTypeDialogProgressListener.prototype = {
 const PREF_BD_USEDOWNLOADDIR = "browser.download.useDownloadDir";
 const nsITimer = Components.interfaces.nsITimer;
 
-let downloadModule = {};
 Components.utils.import("resource://gre/modules/XPCOMUtils.jsm");
-Components.utils.import("resource://gre/modules/DownloadLastDir.jsm", downloadModule);
+Components.utils.import("resource://gre/modules/DownloadLastDir.jsm");
 Components.utils.import("resource://gre/modules/DownloadPaths.jsm");
 Components.utils.import("resource://gre/modules/DownloadUtils.jsm");
 
@@ -246,8 +245,6 @@ nsUnknownContentTypeDialog.prototype = {
     picker.init(parent, windowTitle, nsIFilePicker.modeSave);
     picker.defaultString = aDefaultFile;
 
-    let gDownloadLastDir = new downloadModule.DownloadLastDir(parent);
-
     if (aSuggestedFileExtension) {
       // aSuggestedFileExtension includes the period, so strip it
       picker.defaultExtension = aSuggestedFileExtension.substring(1);
diff --git a/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDir.js b/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDir.js
new file mode 100644
index 00000000000..771ecd23d5f
--- /dev/null
+++ b/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDir.js
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function run_test()
+{
+  let Cc = Components.classes;
+  let Ci = Components.interfaces;
+  let Cu = Components.utils;
+  do_get_profile();
+  Cu.import("resource://gre/modules/DownloadLastDir.jsm");
+
+  function clearHistory() {
+    // simulate clearing the private data
+    Cc["@mozilla.org/observer-service;1"].
+    getService(Ci.nsIObserverService).
+    notifyObservers(null, "browser:purge-session-history", "");
+  }
+
+  do_check_eq(typeof gDownloadLastDir, "object");
+  do_check_eq(gDownloadLastDir.file, null);
+
+  let dirSvc = Cc["@mozilla.org/file/directory_service;1"].
+               getService(Ci.nsIProperties);
+  let tmpDir = dirSvc.get("TmpD", Ci.nsILocalFile);
+  let newDir = tmpDir.clone();
+  newDir.append("testdir" + Math.floor(Math.random() * 10000));
+  newDir.QueryInterface(Ci.nsILocalFile);
+  newDir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
+
+  gDownloadLastDir.file = tmpDir;
+  do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+  do_check_neq(gDownloadLastDir.file, tmpDir);
+
+  gDownloadLastDir.file = 1; // not an nsIFile
+  do_check_eq(gDownloadLastDir.file, null);
+  gDownloadLastDir.file = tmpDir;
+
+  clearHistory();
+  do_check_eq(gDownloadLastDir.file, null);
+  gDownloadLastDir.file = tmpDir;
+
+  let pb;
+  try {
+    pb = Cc["@mozilla.org/privatebrowsing;1"].
+         getService(Ci.nsIPrivateBrowsingService);
+  } catch (e) {
+    print("PB service is not available, bail out");
+    return;
+  }
+
+  let prefs = Cc["@mozilla.org/preferences-service;1"].
+              getService(Ci.nsIPrefBranch);
+  prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
+
+  pb.privateBrowsingEnabled = true;
+  do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+  do_check_neq(gDownloadLastDir.file, tmpDir);
+
+  pb.privateBrowsingEnabled = false;
+  do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+  pb.privateBrowsingEnabled = true;
+
+  gDownloadLastDir.file = newDir;
+  do_check_eq(gDownloadLastDir.file.path, newDir.path);
+  do_check_neq(gDownloadLastDir.file, newDir);
+
+  pb.privateBrowsingEnabled = false;
+  do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+  do_check_neq(gDownloadLastDir.file, tmpDir);
+
+  pb.privateBrowsingEnabled = true;
+  do_check_neq(gDownloadLastDir.file, null);
+  clearHistory();
+  do_check_eq(gDownloadLastDir.file, null);
+
+  pb.privateBrowsingEnabled = false;
+  do_check_eq(gDownloadLastDir.file, null);
+
+  prefs.clearUserPref("browser.privatebrowsing.keep_current_session");
+  newDir.remove(true);
+}
diff --git a/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDirWithCPS.js b/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDirWithCPS.js
new file mode 100644
index 00000000000..983ae9dc332
--- /dev/null
+++ b/toolkit/mozapps/downloads/tests/unit/test_DownloadLastDirWithCPS.js
@@ -0,0 +1,228 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+const Cu = Components.utils;
+
+Cu.import("resource://gre/modules/DownloadLastDir.jsm");
+Cu.import("resource://gre/modules/Services.jsm");
+
+do_get_profile();
+
+function run_test() {
+  function clearHistory() {
+    // simulate clearing the private data
+    Services.obs.notifyObservers(null, "browser:purge-session-history", "");
+  }
+
+  do_check_eq(typeof gDownloadLastDir, "object");
+  do_check_eq(gDownloadLastDir.file, null);
+  
+  let tmpDir = Services.dirsvc.get("TmpD", Ci.nsILocalFile);
+  
+  let uri1 = Services.io.newURI("http://test1.com/", null, null);
+  let uri2 = Services.io.newURI("http://test2.com/", null, null);
+  let uri3 = Services.io.newURI("http://test3.com/", null, null);
+  let uri4 = Services.io.newURI("http://test4.com/", null, null);
+
+  function newDir() {
+    let dir = tmpDir.clone();
+    dir.append("testdir" + Math.floor(Math.random() * 10000));
+    dir.QueryInterface(Ci.nsILocalFile);
+    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
+    return dir;
+  }
+  
+  let dir1 = newDir();
+  let dir2 = newDir();
+  let dir3 = newDir();
+
+  try {
+    { // set up last dir
+      gDownloadLastDir.setFile(null, tmpDir);
+      do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+      do_check_neq(gDownloadLastDir.file, tmpDir);
+    }
+
+    { // set uri1 to dir1, all should now return dir1
+      // also check that a new object is returned
+      gDownloadLastDir.setFile(uri1, dir1);
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_neq(gDownloadLastDir.file, dir1);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path); // set in CPS
+      do_check_neq(gDownloadLastDir.getFile(uri1), dir1);
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir1.path); // fallback
+      do_check_neq(gDownloadLastDir.getFile(uri2), dir1);
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir1.path); // fallback
+      do_check_neq(gDownloadLastDir.getFile(uri3), dir1);
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir1.path); // fallback
+      do_check_neq(gDownloadLastDir.getFile(uri4), dir1);
+    }
+
+    { // set uri2 to dir2, all except uri1 should now return dir2
+      gDownloadLastDir.setFile(uri2, dir2);
+      do_check_eq(gDownloadLastDir.file.path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir2.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir2.path); // fallback
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir2.path); // fallback
+    }
+
+    { // set uri3 to dir3, all except uri1 and uri2 should now return dir3
+      gDownloadLastDir.setFile(uri3, dir3);
+      do_check_eq(gDownloadLastDir.file.path, dir3.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir2.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir3.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir3.path); // fallback
+    }
+
+    { // set uri1 to dir2, all except uri3 should now return dir2
+      gDownloadLastDir.setFile(uri1, dir2);
+      do_check_eq(gDownloadLastDir.file.path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir2.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir2.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir3.path); // set in CPS
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir2.path); // fallback
+    }
+
+    { // check clearHistory removes all data
+      clearHistory();
+      do_check_eq(gDownloadLastDir.file, null);
+      do_check_eq(Services.contentPrefs.hasPref(uri1, "browser.download.lastDir"), false);
+      do_check_eq(gDownloadLastDir.getFile(uri1), null);
+      do_check_eq(gDownloadLastDir.getFile(uri2), null);
+      do_check_eq(gDownloadLastDir.getFile(uri3), null);
+      do_check_eq(gDownloadLastDir.getFile(uri4), null);
+    }
+
+    let pb;
+    try {
+      pb = Cc["@mozilla.org/privatebrowsing;1"].getService(Ci.nsIPrivateBrowsingService);
+    } catch (e) {
+      print("PB service is not available, bail out");
+      return;
+    }
+
+    Services.prefs.setBoolPref("browser.privatebrowsing.keep_current_session", true);
+    
+    { // check data set outside PB mode is remembered
+      gDownloadLastDir.setFile(null, tmpDir);
+      pb.privateBrowsingEnabled = true;
+      do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, tmpDir.path);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, tmpDir.path);
+      
+      clearHistory();
+    }
+
+    { // check data set using CPS outside PB mode is remembered
+      gDownloadLastDir.setFile(uri1, dir1);
+      pb.privateBrowsingEnabled = true;
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+
+      clearHistory();
+    }
+    
+    { // check data set inside PB mode is forgotten
+      pb.privateBrowsingEnabled = true;
+      gDownloadLastDir.setFile(null, tmpDir);
+      do_check_eq(gDownloadLastDir.file.path, tmpDir.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, tmpDir.path);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file, null);
+      do_check_eq(gDownloadLastDir.getFile(uri1), null);
+      
+      clearHistory();
+    }
+    
+    { // check data set using CPS inside PB mode is forgotten
+      pb.privateBrowsingEnabled = true;
+      gDownloadLastDir.setFile(uri1, dir1);
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file, null);
+      do_check_eq(gDownloadLastDir.getFile(uri1), null);
+
+      clearHistory();
+    }
+
+    { // check data set outside PB mode but changed inside is remembered correctly
+      gDownloadLastDir.setFile(uri1, dir1);
+      pb.privateBrowsingEnabled = true;
+      gDownloadLastDir.setFile(uri1, dir2);
+      do_check_eq(gDownloadLastDir.file.path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir2.path);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+
+      // check that the last dir store got cleared
+      pb.privateBrowsingEnabled = true;
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+      
+      pb.privateBrowsingEnabled = false;
+      clearHistory();
+    }
+    
+    { // check clearHistory inside PB mode clears data outside PB mode
+      pb.privateBrowsingEnabled = true;
+      gDownloadLastDir.setFile(uri1, dir2);
+
+      clearHistory();
+      do_check_eq(gDownloadLastDir.file, null);
+      do_check_eq(gDownloadLastDir.getFile(uri1), null);
+
+      pb.privateBrowsingEnabled = false;
+      do_check_eq(gDownloadLastDir.file, null);
+      do_check_eq(gDownloadLastDir.getFile(uri1), null);
+    }
+
+    { // check that disabling CPS works
+      Services.prefs.setBoolPref("browser.download.lastDir.savePerSite", false);
+
+      gDownloadLastDir.setFile(uri1, dir1);
+      do_check_eq(gDownloadLastDir.file.path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir1.path);
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir1.path);
+
+      gDownloadLastDir.setFile(uri2, dir2);
+      do_check_eq(gDownloadLastDir.file.path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri1).path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri2).path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir2.path);
+      do_check_eq(gDownloadLastDir.getFile(uri4).path, dir2.path);
+
+      Services.prefs.clearUserPref("browser.download.lastDir.savePerSite");
+    }
+
+    { // check that passing null to setFile clears the stored value
+      gDownloadLastDir.setFile(uri3, dir3);
+      do_check_eq(gDownloadLastDir.getFile(uri3).path, dir3.path);
+      gDownloadLastDir.setFile(uri3, null);
+      do_check_eq(gDownloadLastDir.getFile(uri3), null);
+    }
+  } finally {
+    dir1.remove(true);
+    dir2.remove(true);
+    dir3.remove(true);
+    Services.prefs.clearUserPref("browser.download.lastDir.savePerSite");
+  }
+}
diff --git a/toolkit/mozapps/downloads/tests/unit/test_privatebrowsing_downloadLastDir.js b/toolkit/mozapps/downloads/tests/unit/test_privatebrowsing_downloadLastDir.js
new file mode 100644
index 00000000000..6248f82c5b2
--- /dev/null
+++ b/toolkit/mozapps/downloads/tests/unit/test_privatebrowsing_downloadLastDir.js
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+const Ci = Components.interfaces;
+const Cc = Components.classes;
+const Cu = Components.utils;
+const Cr = Components.results;
+
+do_get_profile();
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/DownloadLastDir.jsm");
+
+let context = {
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIInterfaceRequestor]),
+  getInterface: XPCOMUtils.generateQI([Ci.nsIDOMWindow])
+};
+
+let launcher = {
+  source: Services.io.newURI("http://test1.com/file", null, null)
+};
+
+Cu.import("resource://test/MockFilePicker.jsm");
+MockFilePicker.init();
+MockFilePicker.returnValue = Ci.nsIFilePicker.returnOK;
+
+function run_test()
+{
+  let pb;
+  try {
+    pb = Cc["@mozilla.org/privatebrowsing;1"].
+         getService(Ci.nsIPrivateBrowsingService);
+  } catch (e) {
+    print("PB service is not available, bail out");
+    return;
+  }
+
+  let prefsService = Cc["@mozilla.org/preferences-service;1"].
+                     getService(Ci.nsIPrefService).
+                     QueryInterface(Ci.nsIPrefBranch);
+  prefsService.setBoolPref("browser.privatebrowsing.keep_current_session", true);
+  let prefs = prefsService.getBranch("browser.download.");
+  let launcherDialog = Cc["@mozilla.org/helperapplauncherdialog;1"].
+                       getService(Ci.nsIHelperAppLauncherDialog);
+  let dirSvc = Cc["@mozilla.org/file/directory_service;1"].
+               getService(Ci.nsIProperties);
+  let tmpDir = dirSvc.get("TmpD", Ci.nsILocalFile);
+  function newDirectory() {
+    let dir = tmpDir.clone();
+    dir.append("testdir" + Math.floor(Math.random() * 10000));
+    dir.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0700);
+    return dir;
+  }
+  function newFileInDirectory(dir) {
+    let file = dir.clone();
+    file.append("testfile" + Math.floor(Math.random() * 10000));
+    file.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0600);
+    return file;
+  }
+  let dir1 = newDirectory();
+  let dir2 = newDirectory();
+  let dir3 = newDirectory();
+  let file1 = newFileInDirectory(dir1);
+  let file2 = newFileInDirectory(dir2);
+  let file3 = newFileInDirectory(dir3);
+
+  prefs.setComplexValue("lastDir", Ci.nsILocalFile, tmpDir);
+
+  MockFilePicker.returnFiles = [file1];
+  let file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
+  do_check_true(!!file);
+  // file picker should start with browser.download.lastDir
+  do_check_eq(MockFilePicker.displayDirectory.path, tmpDir.path);
+  // browser.download.lastDir should be modified before entering the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  // gDownloadLastDir should be usable outside of the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir1.path);
+
+  pb.privateBrowsingEnabled = true;
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  MockFilePicker.returnFiles = [file2];
+  MockFilePicker.displayDirectory = null;
+  file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
+  do_check_true(!!file);
+  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
+  do_check_eq(MockFilePicker.displayDirectory.path, dir1.path);
+  // browser.download.lastDir should not be modified inside the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir1.path);
+  // but gDownloadLastDir should be modified
+  do_check_eq(gDownloadLastDir.file.path, dir2.path);
+
+  pb.privateBrowsingEnabled = false;
+  // gDownloadLastDir should be cleared after leaving the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir1.path);
+  MockFilePicker.returnFiles = [file3];
+  MockFilePicker.displayDirectory = null;
+  file = launcherDialog.promptForSaveToFile(launcher, context, null, null, null);
+  do_check_true(!!file);
+  // file picker should start with browser.download.lastDir as set before entering the private browsing mode
+  do_check_eq(MockFilePicker.displayDirectory.path, dir1.path);
+  // browser.download.lastDir should be modified after leaving the private browsing mode
+  do_check_eq(prefs.getComplexValue("lastDir", Ci.nsILocalFile).path, dir3.path);
+  // gDownloadLastDir should be usable after leaving the private browsing mode
+  do_check_eq(gDownloadLastDir.file.path, dir3.path);
+
+  // cleanup
+  prefsService.clearUserPref("browser.privatebrowsing.keep_current_session");
+  [dir1, dir2, dir3].forEach(function(dir) dir.remove(true));
+
+  MockFilePicker.cleanup();
+}
diff --git a/toolkit/mozapps/downloads/tests/unit/xpcshell.ini b/toolkit/mozapps/downloads/tests/unit/xpcshell.ini
index 8dae3c54e6b..558d009bbf0 100644
--- a/toolkit/mozapps/downloads/tests/unit/xpcshell.ini
+++ b/toolkit/mozapps/downloads/tests/unit/xpcshell.ini
@@ -2,8 +2,11 @@
 head = head_downloads.js
 tail = 
 
+[test_DownloadLastDir.js]
+[test_DownloadLastDirWithCPS.js]
 [test_DownloadPaths.js]
 [test_DownloadUtils.js]
 [test_lowMinutes.js]
+[test_privatebrowsing_downloadLastDir.js]
 [test_syncedDownloadUtils.js]
 [test_unspecified_arguments.js]