Conditionally propagate top controls update to layer tree view.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 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 1699 matching lines @@
 }
 
 void WebViewImpl::setTopControlsHeight(float height, bool topControlsShrinkLayoutSize)
 {
     topControls().setHeight(height, topControlsShrinkLayoutSize);
 }
 
 void WebViewImpl::updateTopControlsState(WebTopControlsState constraint, WebTopControlsState current, bool animate)
 {
     topControls().updateConstraints(constraint);
-    m_layerTreeView->updateTopControlsState(constraint, current, animate);
+    if (m_layerTreeView)
+        m_layerTreeView->updateTopControlsState(constraint, current, animate);
 }
 
 void WebViewImpl::didUpdateTopControls()
 {
     if (m_layerTreeView) {
         m_layerTreeView->setTopControlsShownRatio(topControls().shownRatio());
         m_layerTreeView->setTopControlsHeight(topControls().height(), topControls().shrinkViewport());
     }
 
     WebLocalFrameImpl* mainFrame = mainFrameImpl();
@@ skipping 2888 matching lines @@
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 void WebViewImpl::forceNextWebGLContextCreationToFail()
 {
     WebGLRenderingContext::forceNextWebGLContextCreationToFail();
 }
 
 } // namespace blink