Actually free plugin implement vars when running out of process when the

ppapi/proxy/ppp_class_proxy.h

 // Copyright (c) 2012 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 PPAPI_PROXY_PPP_CLASS_PROXY_H_
 #define PPAPI_PROXY_PPP_CLASS_PROXY_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 68 matching lines @@
                  SerializedVarReceiveInput method_name,
                  SerializedVarVectorReceiveInput arg_vector,
                  SerializedVarOutParam exception,
                  SerializedVarReturnValue result);
   void OnMsgConstruct(int64 ppp_class, int64 object,
                       SerializedVarVectorReceiveInput arg_vector,
                       SerializedVarOutParam exception,
                       SerializedVarReturnValue result);
   void OnMsgDeallocate(int64 ppp_class, int64 object);
 
+  // Returns true if the given class/data points to a plugin-implemented
+  // object. On failure, the exception, if non-NULL, will also be set.
+  bool ValidateUserData(int64 ppp_class, int64 class_data,
+                        SerializedVarOutParam* exception);
+
   DISALLOW_COPY_AND_ASSIGN(PPP_Class_Proxy);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PPP_CLASS_PROXY_H_