cc: Video layers without a frame should not occlude

cc/test/fake_video_frame_provider.h

 // Copyright 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_TEST_FAKE_VIDEO_FRAME_PROVIDER_H_
 #define CC_TEST_FAKE_VIDEO_FRAME_PROVIDER_H_
 
 #include "cc/layers/video_frame_provider.h"
 #include "media/base/video_frame.h"
 
 namespace cc {
 
 // Fake video frame provider that always provides the same VideoFrame.
 class FakeVideoFrameProvider : public VideoFrameProvider {
  public:
   FakeVideoFrameProvider();
   ~FakeVideoFrameProvider() override;
 
   void SetVideoFrameProviderClient(Client* client) override;
   bool UpdateCurrentFrame(base::TimeTicks deadline_min,
                           base::TimeTicks deadline_max) override;
+  bool HasCurrentFrame() override;
   scoped_refptr<media::VideoFrame> GetCurrentFrame() override;
   void PutCurrentFrame() override {}
 
   Client* client() { return client_; }
 
   void set_frame(const scoped_refptr<media::VideoFrame>& frame) {
     frame_ = frame;
   }
 
  private:
   scoped_refptr<media::VideoFrame> frame_;
   Client* client_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_VIDEO_FRAME_PROVIDER_H_