Use macros to define pepper interfaces

ppapi/proxy/ppp_mouse_lock_proxy.h

Index: ppapi/proxy/ppp_mouse_lock_proxy.h
diff --git a/ppapi/proxy/ppp_mouse_lock_proxy.h b/ppapi/proxy/ppp_mouse_lock_proxy.h
index cfd451c1badf060b1e32487f25a778dbc0668538..752e97ae983c9b57b01d45f85fb67d7d4ccc99e8 100644
--- a/ppapi/proxy/ppp_mouse_lock_proxy.h
+++ b/ppapi/proxy/ppp_mouse_lock_proxy.h
@@ -15,21 +15,24 @@ namespace proxy {
 
 class PPP_MouseLock_Proxy : public InterfaceProxy {
  public:
-  PPP_MouseLock_Proxy(Dispatcher* dispatcher, const void* target_interface);
+  PPP_MouseLock_Proxy(Dispatcher* dispatcher);
   virtual ~PPP_MouseLock_Proxy();
 
   static const Info* GetInfo();
 
-  const PPP_MouseLock_Dev* ppp_mouse_lock_target() const {
-    return static_cast<const PPP_MouseLock_Dev*>(target_interface());
-  }
-
   // InterfaceProxy implementation.
   virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
 
  private:
   // Message handlers.
   void OnMsgMouseLockLost(PP_Instance instance);
+
+  // When this proxy is in the plugin side, this value caches the interface
+  // pointer so we don't have to retrieve it from the dispatcher each time.
+  // In the host, this value is always NULL.
+  const PPP_MouseLock_Dev* ppp_mouse_lock_impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(PPP_MouseLock_Proxy);
 };
 
 }  // namespace proxy