Always use the WebFrameWidget when attaching the root graphics

third_party/WebKit/Source/web/tests/FrameTestHelpers.cpp

 /*
  * Copyright (C) 2011 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 291 matching lines @@
     if (type == DetachType::Remove && m_frame->parent())
         m_frame->parent()->removeChild(m_frame);
     m_frame->close();
 }
 
 void TestWebViewClient::initializeLayerTreeView()
 {
     m_layerTreeView = adoptPtr(new WebLayerTreeViewImplForTesting);
 }
 
+void TestWebViewWidgetClient::initializeLayerTreeView()
+{
+    m_testWebViewClient->initializeLayerTreeView();

[dcheng, 2016/06/08 00:10:17]

I don't think I understand why we need this forwarding client: we haven't
removed anything from the public interface.

[lfg, 2016/06/08 21:09:47]

I switched TestWebWidgetClient to be a class instead of an empty implementation
(this was needed because I had to override allowsBrokenNullLayerTreeView() in
tests that needed a frame widget). After that, TestWebViewClient can't be casted
to TestWebWidgetClient anymore, so I added the forwarding code -- it's basically
the same issue we have with WebFrameWidgetImpl/WebViewFrameWidget/WebViewImpl.

+}
+
+WebLayerTreeView* TestWebViewWidgetClient::layerTreeView()
+{
+    return m_testWebViewClient->layerTreeView();
+}
+
+void TestWebViewWidgetClient::scheduleAnimation()
+{
+    m_testWebViewClient->scheduleAnimation();
+}
+
 } // namespace FrameTestHelpers
 } // namespace blink