Proxy PPB_ArrayBuffer_Dev, make them work over Messaging

ppapi/native_client/src/shared/ppapi_proxy/string_proxy_var.h

 // Copyright (c) 2011 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 NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_STRING_PROXY_VAR_H_
 #define NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_STRING_PROXY_VAR_H_
 
 #include "native_client/src/include/nacl_memory.h"
 #include "native_client/src/shared/ppapi_proxy/proxy_var.h"
 
@@ skipping 19 matching lines @@
     if (proxy_var == NULL || proxy_var->pp_var_type() != PP_VARTYPE_STRING) {
       scoped_refptr<StringProxyVar> string_var;
       return string_var;
     }
     return scoped_refptr<StringProxyVar>(
         static_cast<StringProxyVar*>(proxy_var.get()));
   }
 
  private:
   std::string contents_;
-
-  StringProxyVar();  // Not implemented, do not use.
 };
 
 typedef scoped_refptr<StringProxyVar> SharedStringProxyVar;
 
 }  // namespace ppapi_proxy
 
 #endif  // NATIVE_CLIENT_SRC_SHARED_PPAPI_PROXY_STRING_PROXY_VAR_H_