Bug 1180688 - Reset the appropriate widget states if creating a compositor fails. r=mstange

widget/nsBaseWidget.cpp

@@ -1118,6 +1118,10 @@ void nsBaseWidget::CreateCompositor(int aWidth, int aHeight)
   if (!success || !lf) {
     NS_WARNING("Failed to create an OMT compositor.");
     DestroyCompositor();
+    mLayerManager = nullptr;
+    mCompositorChild = nullptr;
+    mCompositorParent = nullptr;
+    mCompositorVsyncDispatcher = nullptr;
     return;
   }