[ChromeOS] Freezes WebUI OOBE/Login window until tab is rendered.

chrome/chrome_browser.gypi

 # 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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'dependencies': [
@@ skipping 733 matching lines @@
         'browser/chromeos/system/syslogs_provider.cc',
         'browser/chromeos/system/syslogs_provider.h',
         'browser/chromeos/system/timezone_settings.cc',
         'browser/chromeos/system/timezone_settings.h',
         'browser/chromeos/system/touchpad_settings.cc',
         'browser/chromeos/system/touchpad_settings.h',
         'browser/chromeos/system_key_event_listener.cc',
         'browser/chromeos/system_key_event_listener.h',
         'browser/chromeos/tab_closeable_state_watcher.cc',
         'browser/chromeos/tab_closeable_state_watcher.h',
+        'browser/chromeos/tab_first_render_watcher.cc',
+        'browser/chromeos/tab_first_render_watcher.h',
         'browser/chromeos/update_observer.cc',
         'browser/chromeos/update_observer.h',
         'browser/chromeos/upgrade_detector_chromeos.cc',
         'browser/chromeos/upgrade_detector_chromeos.h',
         'browser/chromeos/user_cros_settings_provider.cc',
         'browser/chromeos/user_cros_settings_provider.h',
         'browser/chromeos/version_loader.cc',
         'browser/chromeos/version_loader.h',
         'browser/chromeos/view_ids.h',
         'browser/chromeos/views/copy_background.cc',
@@ skipping 4199 matching lines @@
               # weak imports in dependents, who still must #include
               # closure_blocks_leopard_compat.h to get weak imports.
               'type': 'none',
             }],
           ],
         },
       ],
     }],
   ],
 }