Bug 703484 - Part 1c: Disable OMTC on Windows because it crashes. r=bgirard

widget/windows/nsWindow.cpp

@@ -3104,6 +3104,13 @@ GetLayerManagerPrefs(LayerManagerPrefs* aManagerPrefs)
     aManagerPrefs->mDisableAcceleration || safeMode;
 }
 
+bool
+nsWindow::UseOffMainThreadCompositing()
+{
+  // OMTC doesn't work on Windows right now.
+  return false;
+}
+
 LayerManager*
 nsWindow::GetLayerManager(PLayersChild* aShadowManager,
                           LayersBackend aBackendHint,
@@ -3204,9 +3211,7 @@ nsWindow::GetLayerManager(PLayersChild* aShadowManager,
     // Fall back to software if we couldn't use any hardware backends.
     if (!mLayerManager) {
       // Try to use an async compositor first, if possible
-      bool useCompositor =
-        Preferences::GetBool("layers.offmainthreadcomposition.enabled", false);
-      if (useCompositor) {
+      if (UseOffMainThreadCompositing()) {
         // e10s uses the parameter to pass in the shadow manager from the TabChild
         // so we don't expect to see it there since this doesn't support e10s.
         NS_ASSERTION(aShadowManager == nsnull, "Async Compositor not supported with e10s");

widget/windows/nsWindow.h

@@ -275,6 +275,8 @@ public:
   bool                    const DestroyCalled() { return mDestroyCalled; }
 
   static void             SetupKeyModifiersSequence(nsTArray<KeyPair>* aArray, PRUint32 aModifiers);
+
+  virtual bool            UseOffMainThreadCompositing();
 protected:
 
   // A magic number to identify the FAKETRACKPOINTSCROLLABLE window created