Migrate ArcBridgeService::Observer and ArcSession::Observer.

components/arc/test/fake_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_TEST_FAKE_ARC_BRIDGE_SERVICE_H_
 #define COMPONENTS_ARC_TEST_FAKE_ARC_BRIDGE_SERVICE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/arc/arc_bridge_service.h"
 
 namespace arc {
 
 class FakeArcBridgeService : public ArcBridgeService {
  public:
   FakeArcBridgeService();
   ~FakeArcBridgeService() override;
 
   // ArcBridgeService overrides:
   void RequestStart() override;
   void RequestStop() override;
   void OnShutdown() override;
 
   void SetReady();
 
   void SetStopped();
 
-  bool HasObserver(const Observer* observer);
+  bool HasObserver(const ArcSessionObserver* observer);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FakeArcBridgeService);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_TEST_FAKE_ARC_BRIDGE_SERVICE_H_