Add a class to replace ImageLoadingTracker with a nicer API.

chrome/chrome_tests_unit.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': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 712 matching lines @@
         'browser/extensions/extension_sync_data_unittest.cc',
         'browser/extensions/extension_ui_unittest.cc',
         'browser/extensions/extension_warning_badge_service_unittest.cc',
         'browser/extensions/extension_warning_service_unittest.cc',
         'browser/extensions/extensions_quota_service_unittest.cc',
         'browser/extensions/external_policy_loader_unittest.cc',
         'browser/extensions/menu_manager_unittest.cc',
         'browser/extensions/page_action_controller_unittest.cc',
         'browser/extensions/permissions_updater_unittest.cc',
         'browser/extensions/file_reader_unittest.cc',
+        'browser/extensions/image_loader_unittest.cc',
         'browser/extensions/image_loading_tracker_unittest.cc',
         'browser/extensions/key_identifier_conversion_views_unittest.cc',
         'browser/extensions/management_policy_unittest.cc',
         'browser/extensions/process_map_unittest.cc',
         'browser/extensions/sandboxed_unpacker_unittest.cc',
         'browser/extensions/script_badge_controller_unittest.cc',
         'browser/extensions/script_bubble_controller_unittest.cc',
         'browser/extensions/settings/settings_frontend_unittest.cc',
         'browser/extensions/settings/settings_quota_unittest.cc',
         'browser/extensions/settings/settings_sync_unittest.cc',
@@ skipping 1520 matching lines @@
             'unit_tests.isolate',
           ],
           'sources': [
             'unit_tests.isolate',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }