Use expected main frame size from WebViewImpl when creating a new FrameView.

Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 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 492 matching lines @@
     WebLayerTreeView* layerTreeView() const { return m_layerTreeView; }
 
     bool pinchVirtualViewportEnabled() const;
 
     bool matchesHeuristicsForGpuRasterizationForTesting() const { return m_matchesHeuristicsForGpuRasterization; }
 
     virtual void setTopControlsLayoutHeight(float) override;
 
     virtual void forceNextWebGLContextCreationToFail() override;
 
+    IntSize mainFrameSize();
+
 private:
     void didUpdateTopControls();
     void setTopControlsContentOffset(float);
 
     // TODO(bokan): Remains for legacy pinch. Remove once it's gone. Made private to
     // prevent external usage
     virtual void setPageScaleFactor(float scaleFactor, const WebPoint& origin) override;
     void setPageScaleFactorAndLocation(float, const FloatPoint&);
 
     void scrollAndRescaleViewports(float scaleFactor, const IntPoint& mainFrameOrigin, const FloatPoint& pinchViewportOrigin);
@@ skipping 230 matching lines @@
     float m_topControlsLayoutHeight;
 };
 
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 } // namespace blink
 
 #endif