Implement GpuArcVideoService for arc video accelerator

components/arc/video/arc_video_bridge.cc

+// 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.
+
+#include "components/arc/video/arc_video_bridge.h"
+
+#include <utility>
+
+namespace arc {
+
+ArcVideoBridge::ArcVideoBridge(
+    scoped_ptr<VideoHostDelegate> video_host_delegate)
+    : video_host_delegate_(std::move(video_host_delegate)),
+      binding_(video_host_delegate_.get()) {}
+
+ArcVideoBridge::~ArcVideoBridge() {
+  arc::ArcBridgeService* bridge_service = arc::ArcBridgeService::Get();
+  if (bridge_service) {
+    bridge_service->RemoveObserver(this);
+  }
+}
+
+void ArcVideoBridge::StartObservingBridgeServiceChanges() {
+  arc::ArcBridgeService* bridge_service = arc::ArcBridgeService::Get();
+  DCHECK(bridge_service);
+  bridge_service->AddObserver(this);
+
+  // If VideoInstance was ready before we AddObserver(), we won't get
+  // OnVideoInstanceReady events. For such case, we have to call it explicitly.
+  if (bridge_service->video_instance())
+    OnVideoInstanceReady();
+}
+
+void ArcVideoBridge::OnStateChanged(arc::ArcBridgeService::State state) {
+  switch (state) {
+    case arc::ArcBridgeService::State::STOPPING:
+      video_host_delegate_->Shutdown();

[hidehiko, 2016/01/05 08:41:05]

Shutdown() sounds like we will never reuse this (specifically under Chrome's
context). However, we will (specifically after
https://codereview.chromium.org/1548833002/).
How about OnStopping() or something?

[kcwu, 2016/01/06 06:12:41]

Done.

+      break;
+    default:
+      break;
+  }
+}
+
+void ArcVideoBridge::OnVideoInstanceReady() {
+  arc::ArcBridgeService* bridge_service = arc::ArcBridgeService::Get();
+  DCHECK(bridge_service);
+
+  arc::VideoHostPtr host;
+  binding_.Bind(mojo::GetProxy(&host));
+  bridge_service->video_instance()->Init(std::move(host));
+}
+
+}  // namespace arc