arc-bridge: Introduce the ArcService class

components/arc/video/arc_video_bridge.cc

Index: components/arc/video/arc_video_bridge.cc
diff --git a/components/arc/video/arc_video_bridge.cc b/components/arc/video/arc_video_bridge.cc
index dddbb398c9195c0ee2a4008df4d7e2d95c6a415c..bb75506bb36230ff50f12fb9e976702189970537 100644
--- a/components/arc/video/arc_video_bridge.cc
+++ b/components/arc/video/arc_video_bridge.cc
@@ -9,19 +9,10 @@
 namespace arc {
 
 ArcVideoBridge::ArcVideoBridge(
+    ArcBridgeService* bridge_service,
     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();
-  DCHECK(bridge_service);
-  bridge_service->RemoveObserver(this);
-}
-
-void ArcVideoBridge::StartObservingBridgeServiceChanges() {
-  arc::ArcBridgeService* bridge_service = arc::ArcBridgeService::Get();
-  DCHECK(bridge_service);
+      binding_(video_host_delegate_.get()) {
   bridge_service->AddObserver(this);
 
   // If VideoInstance was ready before we AddObserver(), we won't get
@@ -30,6 +21,12 @@ void ArcVideoBridge::StartObservingBridgeServiceChanges() {
     OnVideoInstanceReady();
 }
 
+ArcVideoBridge::~ArcVideoBridge() {
+  arc::ArcBridgeService* bridge_service = arc::ArcBridgeService::Get();
+  DCHECK(bridge_service);
+  bridge_service->RemoveObserver(this);
+}
+
 void ArcVideoBridge::OnStateChanged(arc::ArcBridgeService::State state) {
   switch (state) {
     case arc::ArcBridgeService::State::STOPPING: