Reduce FakeArcBridgeService usage.

components/arc/arc_bridge_service.h

Index: components/arc/arc_bridge_service.h
diff --git a/components/arc/arc_bridge_service.h b/components/arc/arc_bridge_service.h
index 51dede7664420f8929e82cf4d3f5718d778cf8df..d05bd75e6755e6acc493db52ca4863948f580715 100644
--- a/components/arc/arc_bridge_service.h
+++ b/components/arc/arc_bridge_service.h
@@ -88,6 +88,7 @@ class ArcBridgeService {
     virtual ~Observer() {}
   };
 
+  ArcBridgeService();
   virtual ~ArcBridgeService();
 
   // Return true if ARC has been enabled through a commandline
@@ -103,15 +104,15 @@ class ArcBridgeService {
 
   // Starts the ARC service, then it will connect the Mojo channel. When the
   // bridge becomes ready, OnBridgeReady() is called.
-  virtual void RequestStart() = 0;
+  virtual void RequestStart();
 
   // Stops the ARC service.
-  virtual void RequestStop() = 0;
+  virtual void RequestStop();
 
   // OnShutdown() should be called when the browser is shutting down. This can
   // only be called on the thread that this class was created on. We assume that
   // when this function is called, MessageLoop is no longer exists.
-  virtual void OnShutdown() = 0;
+  virtual void OnShutdown();
 
   // Adds or removes observers. This can only be called on the thread that this
   // class was created on. RemoveObserver does nothing if |observer| is not in
@@ -203,8 +204,6 @@ class ArcBridgeService {
     STOPPING,
   };
 
-  ArcBridgeService();
-
   // Instance holders.
   InstanceHolder<mojom::AppInstance> app_;
   InstanceHolder<mojom::AudioInstance> audio_;