NOT FOR COMMIT: sample CL to debug white flashes.

third_party/WebKit/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 4186 matching lines @@
         // be refreshed here when setting a new root layer to avoid being
         // stuck in a presumed incorrectly invisible state.
         m_layerTreeView->setVisible(page()->isPageVisible());
     } else {
         m_rootGraphicsLayer = nullptr;
         m_visualViewportContainerLayer = nullptr;
         m_rootLayer = nullptr;
         // This means that we're transitioning to a new page. Suppress
         // commits until Blink generates invalidations so we don't
         // attempt to paint too early in the next page load.
+        LOG(ERROR) << "Stop painting";
         m_layerTreeView->setDeferCommits(true);
         m_layerTreeView->clearRootLayer();
         visualViewport.clearLayersForTreeView(m_layerTreeView);
     }
 }
 
 void WebViewImpl::invalidateRect(const IntRect& rect)
 {
     if (m_layerTreeView)
         updateLayerTreeViewport();
@@ skipping 286 matching lines @@
     // TODO(jbroman): This is cargo-culted from setRootGraphicsLayer. Is it
     // necessary?
     m_layerTreeView->setVisible(page()->isPageVisible());
 }
 
 void WebViewImpl::detachPaintArtifactCompositor()
 {
     if (!m_layerTreeView)
         return;
 
+    LOG(ERROR) << "Stop painting";
     m_layerTreeView->setDeferCommits(true);
     m_layerTreeView->clearRootLayer();
 }
 
 float WebViewImpl::deviceScaleFactor() const
 {
     // TODO(oshima): Investigate if this should return the ScreenInfo's scale factor rather than
     // page's scale factor, which can be 1 in use-zoom-for-dsf mode.
     if (!page())
         return 1;
 
     return page()->deviceScaleFactor();
 }
 
 } // namespace blink