If a compositing update is declared as needed, scheduleAnimation should be triggered.

Source/web/ChromeClientImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  *
  * 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.
@@ skipping 461 matching lines @@
 void ChromeClientImpl::invalidateContentsForSlowScroll(const IntRect& updateRect)
 {
     invalidateContentsAndRootView(updateRect);
 }
 
 void ChromeClientImpl::scheduleAnimation()
 {
     m_webView->scheduleAnimation();
 }
 
+bool ChromeClientImpl::isCompositorFramePending() const
+{
+    return m_webView->client()->isCompositorFramePending();
+}
+
 void ChromeClientImpl::scroll(
     const IntSize& scrollDelta, const IntRect& scrollRect,
     const IntRect& clipRect)
 {
     if (!m_webView->isAcceleratedCompositingActive()) {
         if (m_webView->client()) {
             int dx = scrollDelta.width();
             int dy = scrollDelta.height();
             m_webView->client()->didScrollRect(dx, dy, intersection(scrollRect, clipRect));
         }
@@ skipping 460 matching lines @@
 {
     return static_cast<NavigatorContentUtilsClient::CustomHandlersState>(m_webView->client()->isProtocolHandlerRegistered(scheme, baseURL, url));
 }
 
 void NavigatorContentUtilsClientImpl::unregisterProtocolHandler(const String& scheme, const WebCore::KURL& baseURL, const WebCore::KURL& url)
 {
     m_webView->client()->unregisterProtocolHandler(scheme, baseURL, url);
 }
 
 } // namespace blink