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

services/video_capture/mojo_shared_memory_buffer_tracker.cc

-// 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.
-
-#include "services/video_capture/mojo_shared_memory_buffer_tracker.h"
-
-#include "base/memory/ptr_util.h"
-#include "services/video_capture/mojo_shared_memory_buffer_handle.h"
-
-namespace video_capture {
-
-MojoSharedMemoryBufferTracker::MojoSharedMemoryBufferTracker()
-    : VideoCaptureBufferTracker() {}
-
-MojoSharedMemoryBufferTracker::~MojoSharedMemoryBufferTracker() = default;
-
-bool MojoSharedMemoryBufferTracker::Init(const gfx::Size& dimensions,
-                                         media::VideoPixelFormat format,
-                                         media::VideoPixelStorage storage_type,
-                                         base::Lock* lock) {
-  if ((format != media::PIXEL_FORMAT_I420) ||
-      (storage_type != media::PIXEL_STORAGE_CPU)) {
-    LOG(ERROR) << "Unsupported pixel format or storage type";
-    return false;
-  }
-
-  set_dimensions(dimensions);
-  set_max_pixel_count(dimensions.GetArea());
-  set_pixel_format(format);
-  set_storage_type(storage_type);
-  mapped_size_ =
-      media::VideoCaptureFormat(dimensions, 0.0f, format, storage_type)
-          .ImageAllocationSize();
-
-  frame_ = media::MojoSharedBufferVideoFrame::CreateDefaultI420(
-      dimensions, base::TimeDelta());
-  return true;
-}
-
-std::unique_ptr<media::VideoCaptureBufferHandle>
-MojoSharedMemoryBufferTracker::GetBufferHandle() {
-  return base::MakeUnique<MojoSharedMemoryBufferHandle>(this);
-}
-
-mojo::ScopedSharedBufferHandle
-MojoSharedMemoryBufferTracker::GetHandleForTransit() {
-  return mojo::ScopedSharedBufferHandle();
-}
-
-}  // namespace video_capture