Enable size_t to int truncation warnings in PPAPI

ppapi/proxy/url_loader_resource.cc

 // 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.
 
 #include "ppapi/proxy/url_loader_resource.h"
 
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 #include "ppapi/c/pp_completion_callback.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/c/ppb_url_loader.h"
 #include "ppapi/proxy/dispatch_reply_message.h"
 #include "ppapi/proxy/file_ref_resource.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/url_request_info_resource.h"
 #include "ppapi/proxy/url_response_info_resource.h"
 #include "ppapi/shared_impl/ppapi_globals.h"
 #include "ppapi/shared_impl/url_response_info_data.h"
@@ skipping 349 matching lines @@
   PP_Resource body_as_file_ref = 0;
   if (data.body_as_file_ref.IsValid()) {
     body_as_file_ref = FileRefResource::CreateFileRef(connection(),
                                                       pp_instance(),
                                                       data.body_as_file_ref);
   }
   response_info_ = new URLResponseInfoResource(
       connection(), pp_instance(), data, body_as_file_ref);
 }
 
-size_t URLLoaderResource::FillUserBuffer() {
+int32_t URLLoaderResource::FillUserBuffer() {
   DCHECK(user_buffer_);
   DCHECK(user_buffer_size_);
 
   size_t bytes_to_copy = std::min(buffer_.size(), user_buffer_size_);
   std::copy(buffer_.begin(), buffer_.begin() + bytes_to_copy, user_buffer_);
   buffer_.erase(buffer_.begin(), buffer_.begin() + bytes_to_copy);
 
   // If the buffer is getting too empty, resume asynchronous loading.
   if (is_asynchronous_load_suspended_ &&
       buffer_.size() <= static_cast<size_t>(
           request_data_.prefetch_buffer_lower_threshold)) {
     DVLOG(1) << "Resuming async load - buffer size: " << buffer_.size();
     SetDefersLoading(false);
   }
 
   // Reset for next time.
   user_buffer_ = NULL;
   user_buffer_size_ = 0;
-  return bytes_to_copy;
+  return base::checked_cast<int32_t>(bytes_to_copy);
 }
 
 }  // namespace proxy
 }  // namespace ppapi