Implement GpuArcVideoService for arc video accelerator

components/arc/video/arc_video_service.h

+// Copyright 2015 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 COMPONENTS_ARC_ARC_VIDEO_SERVICE_H
+#define COMPONENTS_ARC_ARC_VIDEO_SERVICE_H
+
+namespace arc {
+
+// ArcVideoService is an abstract class providing video decoding/encoding
+// acceleration service.
+// The purpose of this class is to create a channel into the GPU process only,
+// which then handles video decoding/encoding, without going through
+// ArcVideoService anymore.
+class ArcVideoService {

[Owen Lin, 2015/12/29 05:31:42]

The document of this class doesn't match to the code. Please see:

https://code.google.com/p/chromium/codesearch#chromium/src/components/arc/pow...

I think this class is in the same role as ArcPowerBridge. To sync with others,
please rename it to ArcVideoBridge.

Besides, I would also suggest that delegating the job of VideoHost to
GpuArcVideoServiceHost, but leave the other implementations here.

More specific:

class ArcVideoBridge : public VideoHost, 
                       public ArcBridgeService::Observer {
  public Initialize() {
     ...
  }

  public onStateChanged() override {
    ... 
  }
}

class GpuArcVideoServiceHost : public ArcVideoBridge {
  public OnRequestArcVideoAcceleratorChannel() override {
  }
}

The responsibilities are clear: ArcVideoBridge handles ArcBridgeService related
things, like registering and state observing. GpuArcVideoServiceHost implements
ArcVideoBridge and mainly provides the VideoHost functions from the GPU process.

[kcwu, 2015/12/29 13:24:43]

Done.

+ public:
+  virtual ~ArcVideoService();
+
+  // Initializes and registers itself to ArcBridgeService.
+  virtual void Initialize() = 0;
+};
+
+}  // namespace arc
+
+#endif  // COMPONENTS_ARC_ARC_VIDEO_SERVICE_H