Add unit tests for ArcBridgeService::RemoveObserver()

components/arc/arc_bridge_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_BRIDGE_SERVICE_H_
 #define COMPONENTS_ARC_ARC_BRIDGE_SERVICE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 159 matching lines @@
   // HandleStartup() should be called upon profile startup.  This will only
   // launch an instance if the instance service is available and it is enabled.
   // This can only be called on the thread that this class was created on.
   virtual void HandleStartup() = 0;
 
   // Shutdown() should be called when the browser is shutting down. This can
   // only be called on the thread that this class was created on.
   virtual void Shutdown() = 0;
 
   // Adds or removes observers. This can only be called on the thread that this
-  // class was created on.
+  // class was created on. RemoveObserver does nothing if |observer| is not in
+  // the list.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
   // Gets the Mojo interface for all the instance services. This will return
   // nullptr if that particular service is not ready yet. Use an Observer if
   // you want to be notified when this is ready. This can only be called on the
   // thread that this class was created on.
   mojom::AppInstance* app_instance() { return app_ptr_.get(); }
   mojom::AudioInstance* audio_instance() { return audio_ptr_.get(); }
   mojom::AuthInstance* auth_instance() { return auth_ptr_.get(); }
@@ skipping 218 matching lines @@
 
   // WeakPtrFactory to use callbacks.
   base::WeakPtrFactory<ArcBridgeService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcBridgeService);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_ARC_BRIDGE_SERVICE_H_