cc: Video layers without a frame should not occlude

cc/layers/video_frame_provider.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 CC_LAYERS_VIDEO_FRAME_PROVIDER_H_
 #define CC_LAYERS_VIDEO_FRAME_PROVIDER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "cc/base/cc_export.h"
@@ skipping 49 matching lines @@
 
   // Called by the client on a regular interval. Returns true if a new frame
   // will be available via GetCurrentFrame() which should be displayed within
   // the presentation interval [|deadline_min|, |deadline_max|].
   //
   // Implementations may use this to drive frame acquisition from underlying
   // sources, so it must be called by clients before calling GetCurrentFrame().
   virtual bool UpdateCurrentFrame(base::TimeTicks deadline_min,
                                   base::TimeTicks deadline_max) = 0;
 
+  virtual bool HasCurrentFrame() const = 0;

[danakj, 2015/05/18 18:15:45]

can you comment what this is?

[hendrikw, 2015/05/18 18:33:59]

Done.

+
   // Returns the current frame, which may have been updated by a recent call to
   // UpdateCurrentFrame(). A call to this method does not ensure that the frame
   // will be rendered. A subsequent call to PutCurrentFrame() must be made if
   // the frame is expected to be rendered.
   //
   // Clients should call this in response to UpdateCurrentFrame() returning true
   // or in response to a DidReceiveFrame() call.
   //
   // TODO(dalecurtis): Remove text about DidReceiveFrame() once the old path
   // has been removed. http://crbug.com/439548
   virtual scoped_refptr<media::VideoFrame> GetCurrentFrame() = 0;
 
   // Indicates that the last frame returned via GetCurrentFrame() is expected to
   // be rendered. Must only occur after a previous call to GetCurrentFrame().
   virtual void PutCurrentFrame() = 0;
 
  protected:
   virtual ~VideoFrameProvider() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_VIDEO_FRAME_PROVIDER_H_