clang/win: Let remaining chromium_code targets build with -Wextra.

chrome/browser/media_galleries/win/mtp_device_delegate_impl_win_unittest.cc

 // Copyright 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 <vector>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 149 matching lines @@
   AttachDevice(StorageInfo::MTP_OR_PTP, "mtp_fake_id", location);
 
   FSInfoMap results;
   MediaFileSystemRegistry* registry =
       g_browser_process->media_file_system_registry();
   registry->GetMediaFileSystemsForExtension(
       web_contents(), extension_.get(),
       base::Bind(&GetGalleryInfoCallback, base::Unretained(&results)));
   base::RunLoop().RunUntilIdle();
 
-  ASSERT_EQ(media_directories_.num_galleries() + 1, results.size());
+  ASSERT_EQ(media_directories_.num_galleries() + 1u, results.size());
   bool checked = false;
   for (FSInfoMap::iterator i = results.begin(); i != results.end(); ++i) {
     MediaFileSystemInfo info = i->second;
     if (info.path == location) {
       CheckGalleryInfo(info, location.LossyDisplayName(), location, true, true);
       checked = true;
       break;
     }
   }
   EXPECT_TRUE(checked);
 }