android webview: Keep zoom methods synchronous

content/public/browser/android/synchronous_compositor.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_PUBLIC_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_H_
 #define CONTENT_PUBLIC_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_H_
 
 #include <stddef.h>
 
 #include "base/memory/ref_counted.h"
@@ skipping 76 matching lines @@
   // Should be called by the embedder after the embedder had modified the
   // scroll offset of the root layer.
   virtual void DidChangeRootLayerScrollOffset(
       const gfx::ScrollOffset& root_offset) = 0;
 
   // Called by the embedder to notify that the compositor is active. The
   // compositor won't ask for vsyncs when it's inactive. NOTE: The compositor
   // starts off as inactive and needs a SetActive(true) call to begin.
   virtual void SetIsActive(bool is_active) = 0;
 
+  // Synchronize all renderer state to UI thread. This blocks the UI thread.
+  virtual void SynchronizeWithRenderer() = 0;
+
   // Called by the embedder to notify that the OnComputeScroll step is happening
   // and if any input animation is active, it should tick now.
   virtual void OnComputeScroll(base::TimeTicks animation_time) = 0;
 
  protected:
   virtual ~SynchronousCompositor() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_ANDROID_SYNCHRONOUS_COMPOSITOR_H_