Make a global enum to differentiate impl & proxy.

ppapi/shared_impl/ppb_input_event_shared.h

Index: ppapi/shared_impl/ppb_input_event_shared.h
diff --git a/ppapi/shared_impl/ppb_input_event_shared.h b/ppapi/shared_impl/ppb_input_event_shared.h
index 1a297506ce21ea2a117dae81d22f4a5d0a36ddbb..77c1028da0117970d8fb33145b95313d04309411 100644
--- a/ppapi/shared_impl/ppb_input_event_shared.h
+++ b/ppapi/shared_impl/ppb_input_event_shared.h
@@ -55,15 +55,7 @@ class PPAPI_SHARED_EXPORT PPB_InputEvent_Shared
     : public Resource,
       public thunk::PPB_InputEvent_API {
  public:
-  struct InitAsImpl {};
-  struct InitAsProxy {};
-
-  // The dummy arguments control which version of Resource's constructor is
-  // called for this base class.
-  PPB_InputEvent_Shared(const InitAsImpl&,
-                        PP_Instance instance,
-                        const InputEventData& data);
-  PPB_InputEvent_Shared(const InitAsProxy&,
+  PPB_InputEvent_Shared(ResourceObjectType type,
                         PP_Instance instance,
                         const InputEventData& data);