[Mojo Video Capture] Simplify media::VideoCaptureDevice::Client:Buffer to a struct

services/video_capture/mojo_shared_memory_buffer_handle.h

-// Copyright 2016 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 SERVICES_VIDEO_CAPTURE_MOJO_SHARED_MEMORY_BUFFER_HANDLE_H_
-#define SERVICES_VIDEO_CAPTURE_MOJO_SHARED_MEMORY_BUFFER_HANDLE_H_
-
-#include "media/capture/video/video_capture_buffer_handle.h"
-#include "media/mojo/common/mojo_shared_buffer_video_frame.h"
-
-namespace video_capture {
-
-class MojoSharedMemoryBufferTracker;
-
-class MojoSharedMemoryBufferHandle : public media::VideoCaptureBufferHandle {
- public:
-  MojoSharedMemoryBufferHandle(MojoSharedMemoryBufferTracker* tracker);
-  ~MojoSharedMemoryBufferHandle() override;
-
-  gfx::Size dimensions() const override;
-  size_t mapped_size() const override;
-  void* data(int plane) override;
-#if defined(OS_POSIX) && !defined(OS_MACOSX)
-  base::FileDescriptor AsPlatformFile() override;
-#endif
-  bool IsBackedByVideoFrame() const override;
-  scoped_refptr<media::VideoFrame> GetVideoFrame() override;
-
- private:
-  MojoSharedMemoryBufferTracker* const tracker_;
-};
-
-}  // namespace video_capture
-
-#endif  // SERVICES_VIDEO_CAPTURE_MOJO_SHARED_MEMORY_BUFFER_HANDLE_H_