[Mojo Video Capture] Adapt video_capture service to refactored video capture stack

media/capture/video/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 MEDIA_CAPTURE_VIDEO_SHARED_MEMORY_BUFFER_HANDLE_H_
+#define MEDIA_CAPTURE_VIDEO_SHARED_MEMORY_BUFFER_HANDLE_H_
+
+#include "media/capture/capture_export.h"
+#include "media/capture/video/video_capture_buffer_handle.h"
+
+namespace media {
+
+// Provides access to memory-mapped shared memory without participating in the
+// lifetime management of the memory. Instances are typically handed out by
+// an instance of VideoCaptureDevice::Client as part of a
+// VideoCaptureDevice::Client::Buffer, which contains a separate
+// |access_permission| that guarantees that the memory stays alive. The buffers
+// are typically managed by an instance of VideoCaptureBufferPool.
+class CAPTURE_EXPORT SharedMemoryBufferHandle
+    : public VideoCaptureBufferHandle {
+ public:
+  explicit SharedMemoryBufferHandle(base::SharedMemory* shared_memory,
+                                    size_t mapped_size);
+  ~SharedMemoryBufferHandle() override;
+
+  size_t mapped_size() const override;
+  uint8_t* data() const override;
+  const uint8_t* const_data() const override;
+
+ private:
+  base::SharedMemory* const shared_memory_;
+  const size_t mapped_size_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_CAPTURE_VIDEO_SHARED_MEMORY_BUFFER_HANDLE_H_