Make a global enum to differentiate impl & proxy.

ppapi/shared_impl/ppb_device_ref_shared.h

Index: ppapi/shared_impl/ppb_device_ref_shared.h
diff --git a/ppapi/shared_impl/ppb_device_ref_shared.h b/ppapi/shared_impl/ppb_device_ref_shared.h
index bbdda72f368ed3097bf16d4e70627b53745cfa2b..908cacea42ed212c549d19487b68e7919ba546f6 100644
--- a/ppapi/shared_impl/ppb_device_ref_shared.h
+++ b/ppapi/shared_impl/ppb_device_ref_shared.h
@@ -29,15 +29,7 @@ class PPAPI_SHARED_EXPORT PPB_DeviceRef_Shared
     : public Resource,
       public thunk::PPB_DeviceRef_API {
  public:
-  struct InitAsImpl {};
-  struct InitAsProxy {};
-
-  // The dummy arguments control which version of Resource's constructor is
-  // called for this base class.
-  PPB_DeviceRef_Shared(const InitAsImpl&,
-                       PP_Instance instance,
-                       const DeviceRefData& data);
-  PPB_DeviceRef_Shared(const InitAsProxy&,
+  PPB_DeviceRef_Shared(ResourceObjectType type,
                        PP_Instance instance,
                        const DeviceRefData& data);