diff --git a/b2g/components/B2GComponents.manifest b/b2g/components/B2GComponents.manifest
index a9cf8b11dd6..87f78260702 100644
--- a/b2g/components/B2GComponents.manifest
+++ b/b2g/components/B2GComponents.manifest
@@ -40,7 +40,8 @@ category app-startup ProcessGlobal service,@mozilla.org/b2g-process-global;1
 
 # ContentHandler.js
 component {d18d0216-d50c-11e1-ba54-efb18d0ef0ac} ContentHandler.js
-contract @mozilla.org/uriloader/content-handler;1?type=application/pdf {d18d0216-d50c-11e1-ba54-efb18d0ef0ac}
+contract @mozilla.org/b2g/activities-content-handler;1 {d18d0216-d50c-11e1-ba54-efb18d0ef0ac}
+category app-startup ContentHandler service,@mozilla.org/b2g/activities-content-handler;1
 
 # PaymentGlue.js
 component {8b83eabc-7929-47f4-8b48-4dea8d887e4b} PaymentGlue.js
diff --git a/b2g/components/ContentHandler.js b/b2g/components/ContentHandler.js
index ec37a51d1c9..38b25fb33f3 100644
--- a/b2g/components/ContentHandler.js
+++ b/b2g/components/ContentHandler.js
@@ -18,22 +18,28 @@ XPCOMUtils.defineLazyGetter(this, "cpmm", function() {
            .getService(Ci.nsIMessageSender);
 });
 
-function log(aMsg) {
-  let msg = "ContentHandler.js: " + (aMsg.join ? aMsg.join("") : aMsg);
-  Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService)
-                                     .logStringMessage(msg);
-  dump(msg + "\n");
+function debug(aMsg) {
+  //dump("--*-- ContentHandler: " + aMsg + "\n");
 }
 
 const NS_ERROR_WONT_HANDLE_CONTENT = 0x805d0001;
-function ContentHandler() {
+
+let ActivityContentFactory = {
+  createInstance: function createInstance(outer, iid) {
+    if (outer != null) {
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    }
+    return new ActivityContentHandler().QueryInterface(iid);
+  },
+
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIFactory])
 }
 
-ContentHandler.prototype = {
-  handleContent: function handleContent(aMimetype, aContext, aRequest) {
-    if (aMimetype != PDF_CONTENT_TYPE)
-      throw NS_ERROR_WONT_HANDLE_CONTENT;
+function ActivityContentHandler() {
+}
 
+ActivityContentHandler.prototype = {
+  handleContent: function handleContent(aMimetype, aContext, aRequest) {
     if (!(aRequest instanceof Ci.nsIChannel))
       throw NS_ERROR_WONT_HANDLE_CONTENT;
 
@@ -46,8 +52,96 @@ ContentHandler.prototype = {
     aRequest.cancel(Cr.NS_BINDING_ABORTED);
   },
 
-  classID: Components.ID("{d18d0216-d50c-11e1-ba54-efb18d0ef0ac}"),
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIContentHandler])
+}
+
+function ContentHandler() {
+  this.classIdMap = {};
+}
+
+ContentHandler.prototype = {
+  observe: function(aSubject, aTopic, aData) {
+    if (aTopic == "app-startup") {
+      // We only want to register these from content processes.
+      let appInfo = Cc["@mozilla.org/xre/app-info;1"];
+      if (appInfo.getService(Ci.nsIXULRuntime)
+          .processType == Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
+        return;
+      }
+    }
+
+    cpmm.addMessageListener("Activities:RegisterContentTypes", this);
+    cpmm.addMessageListener("Activities:UnregisterContentTypes", this);
+    cpmm.sendAsyncMessage("Activities:GetContentTypes", { });
+  },
+
+  /**
+    * Do the component registration for a content type.
+    * We only need to register one component per content type, even if several
+    * apps provide it, so we keep track of the number of providers for each
+    * content type.
+    */
+  registerContentHandler: function registerContentHandler(aContentType) {
+    debug("Registering " + aContentType);
+
+    // We already have a provider for this content type, just increase the
+    // tracking count.
+    if (this.classIdMap[aContentType]) {
+      this.classIdMap[aContentType].count++;
+      return;
+    }
+
+    let contractID = "@mozilla.org/uriloader/content-handler;1?type=" +
+                     aContentType;
+    let uuidGen = Cc["@mozilla.org/uuid-generator;1"]
+                    .getService(Ci.nsIUUIDGenerator);
+    let id = Components.ID(uuidGen.generateUUID().toString());
+    this.classIdMap[aContentType] = { count: 1, id: id };
+    let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+    cr.registerFactory(Components.ID(id), "Activity Content Handler", contractID,
+                       ActivityContentFactory);
+  },
+
+  /**
+    * Do the component unregistration for a content type.
+    */
+  unregisterContentHandler: function registerContentHandler(aContentType) {
+    debug("Unregistering " + aContentType);
+
+    let record = this.classIdMap[aContentType];
+    if (!record) {
+      return;
+    }
+
+    // Bail out if we still have providers left for this content type.
+    if (--record.count > 0) {
+      return;
+    }
+
+    let contractID = "@mozilla.org/uriloader/content-handler;1?type=" +
+                     aContentType;
+    let cr = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+    cr.unregisterFactory(record.id, ActivityContentFactory);
+    delete this.classIdMap[aContentType]
+  },
+
+  receiveMessage: function(aMessage) {
+    let data = aMessage.data;
+
+    switch (aMessage.name) {
+      case "Activities:RegisterContentTypes":
+        data.contentTypes.forEach(this.registerContentHandler, this);
+        break;
+      case "Activities:UnregisterContentTypes":
+        data.contentTypes.forEach(this.unregisterContentHandler, this);
+        break;
+    }
+  },
+
+  classID: Components.ID("{d18d0216-d50c-11e1-ba54-efb18d0ef0ac}"),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsIContentHandler,
+                                         Ci.nsIObserver,
+                                         Ci.nsISupportsWeakReference])
 };
 
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([ContentHandler]);
diff --git a/dom/activities/src/ActivitiesService.jsm b/dom/activities/src/ActivitiesService.jsm
index 955e0081b23..c3688b7f9cb 100644
--- a/dom/activities/src/ActivitiesService.jsm
+++ b/dom/activities/src/ActivitiesService.jsm
@@ -17,6 +17,10 @@ XPCOMUtils.defineLazyServiceGetter(this, "ppmm",
                                    "@mozilla.org/parentprocessmessagemanager;1",
                                    "nsIMessageBroadcaster");
 
+XPCOMUtils.defineLazyServiceGetter(this, "NetUtil",
+                                   "@mozilla.org/network/util;1",
+                                   "nsINetUtil");
+
 this.EXPORTED_SYMBOLS = [];
 
 let idbGlobal = this;
@@ -158,6 +162,7 @@ let Activities = {
 
     "Activities:Register",
     "Activities:Unregister",
+    "Activities:GetContentTypes"
   ],
 
   init: function activities_init() {
@@ -311,9 +316,18 @@ let Activities = {
         break;
 
       case "Activities:Register":
+        let self = this;
         this.db.add(msg,
           function onSuccess(aEvent) {
             mm.sendAsyncMessage("Activities:Register:OK", null);
+            let res = [];
+            msg.forEach(function(aActivity) {
+              self.updateContentTypeList(aActivity, res);
+            });
+            if (res.length) {
+              ppmm.broadcastAsyncMessage("Activities:RegisterContentTypes",
+                                         { contentTypes: res });
+            }
           },
           function onError(aEvent) {
             msg.error = "REGISTER_ERROR";
@@ -322,8 +336,60 @@ let Activities = {
         break;
       case "Activities:Unregister":
         this.db.remove(msg);
+        let res = [];
+        msg.forEach(function(aActivity) {
+          this.updateContentTypeList(aActivity, res);
+        }, this);
+        if (res.length) {
+          ppmm.broadcastAsyncMessage("Activities:UnregisterContentTypes",
+                                     { contentTypes: res });
+        }
+        break;
+      case "Activities:GetContentTypes":
+        this.sendContentTypes(mm);
         break;
     }
+  },
+
+  updateContentTypeList: function updateContentTypeList(aActivity, aResult) {
+    // Bail out if this is not a "view" activity.
+    if (aActivity.name != "view") {
+      return;
+    }
+
+    let types = aActivity.description.filters.type;
+    if (typeof types == "string") {
+      types = [types];
+    }
+
+    // Check that this is a real content type and sanitize it.
+    types.forEach(function(aContentType) {
+      let hadCharset = { };
+      let charset = { };
+      let contentType =
+        NetUtil.parseContentType(aContentType, charset, hadCharset);
+      if (contentType) {
+        aResult.push(contentType);
+      }
+    });
+  },
+
+  sendContentTypes: function sendContentTypes(aMm) {
+    let res = [];
+    let self = this;
+    this.db.find({ options: { name: "view" } },
+      function() { // Success callback.
+        if (res.length) {
+          aMm.sendAsyncMessage("Activities:RegisterContentTypes",
+                               { contentTypes: res });
+        }
+      },
+      null, // Error callback.
+      function(aActivity) { // Matching callback.
+        self.updateContentTypeList(aActivity, res)
+        return false;
+      }
+    );
   }
 }
 
diff --git a/dom/apps/src/Webapps.jsm b/dom/apps/src/Webapps.jsm
index 7f1f66099f6..143b8c6abaf 100644
--- a/dom/apps/src/Webapps.jsm
+++ b/dom/apps/src/Webapps.jsm
@@ -688,7 +688,8 @@ this.DOMApplicationRegistry = {
     for (let activity in root.activities) {
       let description = root.activities[activity];
       activitiesToUnregister.push({ "manifest": aApp.manifestURL,
-                                    "name": activity });
+                                    "name": activity,
+                                    "description": description });
     }
     return activitiesToUnregister;
   },