Enable size_t to int truncation warnings in PPAPI

ppapi/proxy/url_loader_resource.h

 // Copyright (c) 2013 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_URL_LOADER_RESOURCE_H_
 #define PPAPI_PROXY_URL_LOADER_RESOURCE_H_
 
 #include <deque>
 
 #include "base/basictypes.h"
@@ skipping 96 matching lines @@
   // Sets up |callback| as the pending callback. This should only be called once
   // it is certain that |PP_OK_COMPLETIONPENDING| will be returned.
   void RegisterCallback(scoped_refptr<TrackedCallback> callback);
 
   void RunCallback(int32_t result);
 
   // Saves the given response info to response_info_, handling file refs if
   // necessary. This does not issue any callbacks.
   void SaveResponseInfo(const URLResponseInfoData& data);
 
-  size_t FillUserBuffer();
+  int32_t FillUserBuffer();
 
   Mode mode_;
   URLRequestInfoData request_data_;
 
   scoped_refptr<TrackedCallback> pending_callback_;
 
   PP_URLLoaderTrusted_StatusCallback status_callback_;
 
   std::deque<char> buffer_;
   int64_t bytes_sent_;
   int64_t total_bytes_to_be_sent_;
   int64_t bytes_received_;
   int64_t total_bytes_to_be_received_;
   char* user_buffer_;
   size_t user_buffer_size_;
   int32_t done_status_;
   bool is_streaming_to_file_;
   bool is_asynchronous_load_suspended_;
 
   // The response info if we've received it.
   scoped_refptr<URLResponseInfoResource> response_info_;
 
   DISALLOW_COPY_AND_ASSIGN(URLLoaderResource);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_URL_LOADER_RESOURCE_H_