Change extension icon load errors to warnings

chrome/chrome_tests_unit.gypi

 # Copyright 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.
 {
   'variables': {
     'chrome_unit_tests_sources': [
       # histograms.xml is analyzed by AboutFlagsHistogramTest, so this
       # dependency is needed to make commit bots run unit_tests on
       # histograms.xml changes.
       '../tools/metrics/histograms/histograms.xml',
@@ skipping 603 matching lines @@
       'browser/extensions/api/declarative_webrequest/webrequest_action_unittest.cc',
       'browser/extensions/api/declarative_webrequest/webrequest_rules_registry_unittest.cc',
       'browser/extensions/api/developer_private/developer_private_api_unittest.cc',
       'browser/extensions/api/developer_private/extension_info_generator_unittest.cc',
       'browser/extensions/api/device_permissions_manager_unittest.cc',
       'browser/extensions/api/dial/dial_device_data_unittest.cc',
       'browser/extensions/api/dial/dial_registry_unittest.cc',
       'browser/extensions/api/dial/dial_service_unittest.cc',
       'browser/extensions/api/easy_unlock_private/easy_unlock_private_api_chromeos_unittest.cc',
       'browser/extensions/api/experience_sampling_private/experience_sampling_private_api_unittest.cc',
+      'browser/extensions/api/extension_action/browser_action_unittest.cc',
       'browser/extensions/api/extension_action/extension_action_prefs_unittest.cc',
       'browser/extensions/api/file_handlers/api_file_handler_util_unittest.cc',
       'browser/extensions/api/file_handlers/mime_util_unittest.cc',
       'browser/extensions/api/file_system/file_system_api_unittest.cc',
       'browser/extensions/api/gcd_private/privet_v3_context_getter_unittest.cc',
       'browser/extensions/api/gcd_private/privet_v3_session_unittest.cc',
       'browser/extensions/api/identity/extension_token_key_unittest.cc',
       'browser/extensions/api/identity/gaia_web_auth_flow_unittest.cc',
       'browser/extensions/api/identity/identity_mint_queue_unittest.cc',
       'browser/extensions/api/image_writer_private/destroy_partitions_operation_unittest.cc',
@@ skipping 2385 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }