Expose locks for CopyFromCompositingSurface/CopyFromBackingStore API

content/port/browser/render_widget_host_view_port.h

 // Copyright (c) 2012 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_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_
 #define CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 166 matching lines @@
   // be initialized even on failure.
   // A smaller region than |src_subrect| may be copied if the underlying surface
   // is smaller than |src_subrect|.
   // NOTE: |callback| is called asynchronously.
   virtual void CopyFromCompositingSurface(
       const gfx::Rect& src_subrect,
       const gfx::Size& dst_size,
       const base::Callback<void(bool, const SkBitmap&)>& callback,
       const SkBitmap::Config config) = 0;
 
+  // For async implementation of copy, we provide a lock to ensure that the
+  // content is not evicted while copying.

[no sievers, 2014/02/21 02:34:10]

I'd say that it instructs the view to not drop the surface even when the view is
hidden.

I'd also put a comment in the public interface.

[powei, 2014/02/21 18:41:15]

Done.

+  virtual void LockSurfaceForCopy() = 0;
+  virtual void UnlockSurfaceForCopy() = 0;
+
   // Copies a given subset of the compositing surface's content into a YV12
   // VideoFrame, and invokes a callback with a success/fail parameter. |target|
   // must contain an allocated, YV12 video frame of the intended size. If the
   // copy rectangle does not match |target|'s size, the copied content will be
   // scaled and letterboxed with black borders. The copy will happen
   // asynchronously. This operation will fail if there is no available
   // compositing surface.
   virtual void CopyFromCompositingSurfaceToVideoFrame(
       const gfx::Rect& src_subrect,
       const scoped_refptr<media::VideoFrame>& target,
@@ skipping 149 matching lines @@
 
   // Returns an HWND that's given as the parent window for windowless Flash to
   // workaround crbug.com/301548.
   virtual gfx::NativeViewId GetParentForWindowlessPlugin() const = 0;
 #endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PORT_BROWSER_RENDER_WIDGET_HOST_VIEW_PORT_H_