Fix shutdown assertions in WebViewImpl

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 3973 matching lines @@
 
     m_page->settings().setAcceleratedCompositingEnabled(m_layerTreeView != 0);
 
     // FIXME: only unittests, click to play, Android priting, and printing (for headers and footers)
     // make this assert necessary. We should make them not hit this code and then delete allowsBrokenNullLayerTreeView.
     ASSERT(m_layerTreeView || !m_client || m_client->allowsBrokenNullLayerTreeView());
 }
 
 void WebViewImpl::setIsAcceleratedCompositingActive(bool active)
 {
+    // In the middle of shutting down; don't try to spin back up a compositor.
+    // FIXME: compositing startup/shutdown should be refactored so that it
+    // turns on explicitly rather than lazily, which causes this awkwardness.
+    if (m_layerTreeViewClosed)
+        return;
+
     ASSERT(!active || m_layerTreeView);
     blink::Platform::current()->histogramEnumeration("GPU.setIsAcceleratedCompositingActive", active * 2 + m_isAcceleratedCompositingActive, 4);
 
     if (m_isAcceleratedCompositingActive == active)
         return;
 
     if (!m_client)
         return;
 
-    // In the middle of shutting down; don't try to spin back up a compositor.
-    if (m_layerTreeViewClosed)
-        return;
-
     if (!active) {
         m_isAcceleratedCompositingActive = false;
         if (!m_layerTreeViewCommitsDeferred) {
             ASSERT(m_layerTreeView);
             // This means that we're transitioning to a new page. Suppress commits until WebKit generates invalidations so
             // we don't attempt to paint too early in the next page load.
             m_layerTreeView->setDeferCommits(true);
             m_layerTreeViewCommitsDeferred = true;
         }
     } else {
@@ skipping 218 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink