Don't schedule an animation during compositing dirty-bit setting unless needed.

Source/web/PageWidgetDelegate.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 50 matching lines @@
 {
     RefPtr<FrameView> view = mainFrameView(page);
     if (!view)
         return;
     page->autoscrollController().animate(monotonicFrameBeginTime);
     page->animator().serviceScriptedAnimations(monotonicFrameBeginTime);
 }
 
 void PageWidgetDelegate::layout(Page* page)
 {
-    RefPtr<FrameView> view = mainFrameView(page);
-    if (!view)
+    if (!page || !page->mainFrame())
         return;
-    // In order for our child HWNDs (NativeWindowWidgets) to update properly,
-    // they need to be told that we are updating the screen. The problem is that
-    // the native widgets need to recalculate their clip region and not overlap
-    // any of our non-native widgets. To force the resizing, call
-    // setFrameRect(). This will be a quick operation for most frames, but the
-    // NativeWindowWidgets will update a proper clipping region.
-    view->setFrameRect(view->frameRect());
-
-    // setFrameRect may have the side-effect of causing existing page layout to
-    // be invalidated, so layout needs to be called last.
-    view->updateLayoutAndStyleForPainting();
+    page->animator().updateLayoutAndStyleForPainting();
 }
 
 void PageWidgetDelegate::paint(Page* page, PageOverlayList* overlays, WebCanvas* canvas, const WebRect& rect, CanvasBackground background)
 {
     if (rect.isEmpty())
         return;
     GraphicsContext gc(canvas);
     gc.setCertainlyOpaque(background == Opaque);
     gc.applyDeviceScaleFactor(page->deviceScaleFactor());
     gc.setUseHighResMarkers(page->deviceScaleFactor() > 1.5f);
@@ skipping 118 matching lines @@
 {
     return mainFrame.eventHandler().handleWheelEvent(PlatformWheelEventBuilder(mainFrame.view(), event));
 }
 
 bool PageWidgetEventHandler::handleTouchEvent(LocalFrame& mainFrame, const WebTouchEvent& event)
 {
     return mainFrame.eventHandler().handleTouchEvent(PlatformTouchEventBuilder(mainFrame.view(), event));
 }
 
 }