Enable size_t to int truncation warnings in PPAPI

ppapi/tests/test_file_mapping.cc

 // Copyright 2014 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/tests/test_file_mapping.h"
 
 #include <string.h>
 
 #include <limits>
 #include <string>
@@ skipping 37 matching lines @@
 }
 
 int32_t WriteEntireBuffer(PP_Instance instance,
                           pp::FileIO* file_io,
                           int32_t offset,
                           const std::string& data,
                           CallbackType callback_type) {
   TestCompletionCallback callback(instance, callback_type);
   int32_t write_offset = offset;
   const char* buf = data.c_str();
-  int32_t size = data.size();
+  int32_t size = static_cast<int32_t>(data.size());
 
   while (write_offset < offset + size) {
     callback.WaitForResult(file_io->Write(write_offset,
                                           &buf[write_offset - offset],
                                           size - write_offset + offset,
                                           callback.GetCallback()));
     if (callback.result() < 0)
       return callback.result();
     if (callback.result() == 0)
       return PP_ERROR_FAILED;
@@ skipping 461 matching lines @@
                                   0,
                                   &new_file_contents2,
                                   callback_type()));
   ASSERT_EQ(expected_file_contents2, new_file_contents2);
 
   // TODO(dmichael): Test non-zero offset
 
   PASS();
 }