Use macros to define pepper interfaces

ppapi/proxy/ppb_testing_proxy.h

Index: ppapi/proxy/ppb_testing_proxy.h
diff --git a/ppapi/proxy/ppb_testing_proxy.h b/ppapi/proxy/ppb_testing_proxy.h
index c07f6a9495f9570214e2de50440958c131f42db3..eaf5fb31858d8f0a721156d276c8c61c41c092f4 100644
--- a/ppapi/proxy/ppb_testing_proxy.h
+++ b/ppapi/proxy/ppb_testing_proxy.h
@@ -19,15 +19,11 @@ namespace proxy {
 
 class PPB_Testing_Proxy : public InterfaceProxy {
  public:
-  PPB_Testing_Proxy(Dispatcher* dispatcher, const void* target_interface);
+  PPB_Testing_Proxy(Dispatcher* dispatcher);
   virtual ~PPB_Testing_Proxy();
 
   static const Info* GetInfo();
 
-  const PPB_Testing_Dev* ppb_testing_target() const {
-    return static_cast<const PPB_Testing_Dev*>(target_interface());
-  }
-
   // InterfaceProxy implementation.
   virtual bool OnMessageReceived(const IPC::Message& msg);
 
@@ -41,6 +37,11 @@ class PPB_Testing_Proxy : public InterfaceProxy {
   void OnMsgQuitMessageLoop(PP_Instance instance);
   void OnMsgGetLiveObjectsForInstance(PP_Instance instance, uint32_t* result);
 
+  // When this proxy is in the host side, this value caches the interface
+  // pointer so we don't have to retrieve it from the dispatcher each time.
+  // In the plugin, this value is always NULL.
+  const PPB_Testing_Dev* ppb_testing_impl_;
+
   DISALLOW_COPY_AND_ASSIGN(PPB_Testing_Proxy);
 };