diff --git a/CLOBBER b/CLOBBER
index c591cfb0079..934512f49ee 100644
--- a/CLOBBER
+++ b/CLOBBER
@@ -22,4 +22,4 @@
 # changes to stick? As of bug 928195, this shouldn't be necessary! Please
 # don't change CLOBBER for WebIDL changes any more.
 
-Bug 917322 - Due to removing nsICompositionStringSynthesizer.idl
+Bug 1123384 - Needs a clobber for some reason.
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index e3dbfdb5800..c8d03dd35f5 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -58,7 +58,6 @@
 #include "nsContentCID.h"
 #include "nsLayoutStatics.h"
 #include "nsCCUncollectableMarker.h"
-#include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/workers/Workers.h"
 #include "mozilla/dom/MessagePortList.h"
 #include "mozilla/dom/ToJSValue.h"
@@ -563,36 +562,6 @@ nsTimeout::HasRefCntOne()
   return mRefCnt.get() == 1;
 }
 
-// We use only 53 bits for the window ID so that it can be converted to and from
-// a JS value without loss of precision. The upper bits of the window ID hold the
-// process ID. The lower bits identify the window.
-static const uint64_t kWindowIDTotalBits = 53;
-static const uint64_t kWindowIDProcessBits = 22;
-static const uint64_t kWindowIDWindowBits = kWindowIDTotalBits - kWindowIDProcessBits;
-
-// Try to return a window ID that is unique across processes and that will never
-// be recycled.
-static uint64_t
-NextWindowID()
-{
-  uint64_t processID = 0;
-  if (XRE_GetProcessType() == GeckoProcessType_Content) {
-    ContentChild* cc = ContentChild::GetSingleton();
-    processID = cc->GetID();
-  }
-
-  MOZ_RELEASE_ASSERT(processID < (uint64_t(1) << kWindowIDProcessBits));
-  uint64_t processBits = processID & ((uint64_t(1) << kWindowIDProcessBits) - 1);
-
-  // Make sure no actual window ends up with mWindowID == 0.
-  uint64_t windowID = ++gNextWindowID;
-
-  MOZ_RELEASE_ASSERT(windowID < (uint64_t(1) << kWindowIDWindowBits));
-  uint64_t windowBits = windowID & ((uint64_t(1) << kWindowIDWindowBits) - 1);
-
-  return (processBits << kWindowIDWindowBits) | windowBits;
-}
-
 nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
 : mFrameElement(nullptr), mDocShell(nullptr), mModalStateDepth(0),
   mRunningTimeout(nullptr), mMutationBits(0), mIsDocumentLoaded(false),
@@ -607,7 +576,7 @@ nsPIDOMWindow::nsPIDOMWindow(nsPIDOMWindow *aOuterWindow)
   mAudioMuted(false), mAudioVolume(1.0),
   mInnerWindow(nullptr), mOuterWindow(aOuterWindow),
   // Make sure no actual window ends up with mWindowID == 0
-  mWindowID(NextWindowID()), mHasNotifiedGlobalCreated(false),
+  mWindowID(++gNextWindowID), mHasNotifiedGlobalCreated(false),
   mMarkedCCGeneration(0), mSendAfterRemotePaint(false)
  {}