arc: Revamp the ArcBridgeService interface

components/arc/clipboard/arc_clipboard_bridge.h

 // Copyright 2016 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_CLIPBOARD_ARC_CLIPBOARD_BRIDGE_H_
 #define COMPONENTS_ARC_CLIPBOARD_ARC_CLIPBOARD_BRIDGE_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "components/arc/arc_bridge_service.h"
 #include "components/arc/arc_service.h"
+#include "components/arc/instance_holder.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace arc {
 
-class ArcClipboardBridge : public ArcService,
-                           public ArcBridgeService::Observer,
-                           public mojom::ClipboardHost {
+class ArcClipboardBridge
+    : public ArcService,
+      public InstanceHolder<mojom::ClipboardInstance>::Observer,
+      public mojom::ClipboardHost {
  public:
   explicit ArcClipboardBridge(ArcBridgeService* bridge_service);
   ~ArcClipboardBridge() override;
 
-  // ArcBridgeService::Observer overrides.
-  void OnClipboardInstanceReady() override;
+  // InstanceHolder<mojom::ClipboardInstance>::Observer overrides.
+  void OnInstanceReady() override;
 
   // mojom::ClipboardHost overrides.
   void SetTextContent(const mojo::String& text) override;
   void GetTextContent() override;
 
  private:
   bool CalledOnValidThread();
 
   mojo::Binding<mojom::ClipboardHost> binding_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcClipboardBridge);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_CLIPBOARD_ARC_CLIPBOARD_BRIDGE_H_