Avoid rotation anchor during transitional fullscreen states.

third_party/WebKit/Source/web/FullscreenController.h

 /*
  * Copyright (C) 2013 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 42 matching lines @@
   // Called by content::RenderWidget (via WebWidget) to notify that we've
   // entered or exited fullscreen. This can be because we requested it, or it
   // can be initiated by the browser directly.
   void didEnterFullscreen();
   void didExitFullscreen();
 
   // Called by Fullscreen (via ChromeClient) to notify that the fullscreen
   // element has changed.
   void fullscreenElementChanged(Element*, Element*);
 
-  bool isFullscreen() { return m_state == State::Fullscreen; }
+  bool isFullscreen() { return m_state != State::Initial; }

[mlamouri (slow - plz ping), 2017/03/13 21:00:56]

nit: should it be renamed "isFullscreenOrTransitionning() const"?

 
   void updateSize();
 
   void didUpdateLayout();
 
  protected:
   explicit FullscreenController(WebViewImpl*);
 
  private:
   void updatePageScaleConstraints(bool removeConstraints);
@@ skipping 18 matching lines @@
   State m_state = State::Initial;
 
   float m_initialPageScaleFactor = 0.0f;
   IntSize m_initialScrollOffset;
   FloatPoint m_initialVisualViewportOffset;
 };
 
 }  // namespace blink
 
 #endif