Re-land alexbost's experimental Offscreen Tabs API work.

chrome/chrome_browser.gypi

 # Copyright (c) 2012 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',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 1097 matching lines @@
         'browser/extensions/extension_message_handler.cc',
         'browser/extensions/extension_message_handler.h',
         'browser/extensions/extension_message_service.cc',
         'browser/extensions/extension_message_service.h',
         'browser/extensions/extension_metrics_module.cc',
         'browser/extensions/extension_metrics_module.h',
         'browser/extensions/extension_module.cc',
         'browser/extensions/extension_module.h',
         'browser/extensions/extension_navigation_observer.cc',
         'browser/extensions/extension_navigation_observer.h',
+        'browser/extensions/extension_offscreen_tabs_module.cc',
+        'browser/extensions/extension_offscreen_tabs_module.h',
+        'browser/extensions/extension_offscreen_tabs_module_constants.cc',
+        'browser/extensions/extension_offscreen_tabs_module_constants.h',
         'browser/extensions/extension_omnibox_api.cc',
         'browser/extensions/extension_omnibox_api.h',
         'browser/extensions/extension_page_actions_module.cc',
         'browser/extensions/extension_page_actions_module.h',
         'browser/extensions/extension_page_actions_module_constants.cc',
         'browser/extensions/extension_page_actions_module_constants.h',
         'browser/extensions/extension_page_capture_api.cc',
         'browser/extensions/extension_page_capture_api.h',
         'browser/extensions/extension_pref_store.cc',
         'browser/extensions/extension_pref_store.h',
@@ skipping 4348 matching lines @@
       'type': 'static_library',
       'sources': [ 'browser/history/in_memory_url_index_cache.proto' ],
       'variables': {
         'proto_in_dir': 'browser/history',
         'proto_out_dir': 'chrome/browser/history',
       },
       'includes': [ '../build/protoc.gypi' ]
     },
   ],
 }