Refactor ArcBridgeService detection and initialization to a separate class ArcServiceLauncher.

components/arc/arc_bridge_service_impl.h

Index: components/arc/arc_bridge_service_impl.h
diff --git a/components/arc/arc_bridge_service_impl.h b/components/arc/arc_bridge_service_impl.h
index ea90b0872762f8dc56ae63988e0391b2a719f2c7..1d884ff45860c06c86b0573fd52b1cb812690f64 100644
--- a/components/arc/arc_bridge_service_impl.h
+++ b/components/arc/arc_bridge_service_impl.h
@@ -29,7 +29,7 @@ class ArcBridgeServiceImpl : public ArcBridgeService,
   explicit ArcBridgeServiceImpl(scoped_ptr<ArcBridgeBootstrap> bootstrap);
   ~ArcBridgeServiceImpl() override;
 
-  void DetectAvailability() override;
+  void SetDetectedAvailability(bool available) override;
 
   void HandleStartup() override;
 
@@ -51,9 +51,6 @@ class ArcBridgeServiceImpl : public ArcBridgeService,
   void OnConnectionEstablished(ArcBridgeInstancePtr instance) override;
   void OnStopped() override;
 
-  // DBus callbacks.
-  void OnArcAvailable(bool available);
-
   // Called when the bridge channel is closed. This typically only happens when
   // the ARC instance crashes. This is not called during shutdown.
   void OnChannelClosed();