Add initial browsertest of download notification

chrome/chrome_tests.gypi

 # 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.
 {
   'variables': {
     'chrome_browser_extensions_test_support_sources': [
       # A list of sources which is shared between different browser tests.
       'browser/apps/app_browsertest_util.cc',
       'browser/apps/app_browsertest_util.h',
       'browser/extensions/browsertest_util.cc',
@@ skipping 731 matching lines @@
       'browser/chromeos/policy/power_policy_browsertest.cc',
       'browser/chromeos/policy/user_cloud_external_data_manager_browsertest.cc',
       'browser/chromeos/policy/user_cloud_policy_manager_chromeos_browsertest.cc',
       'browser/chromeos/policy/variations_service_policy_browsertest.cc',
       'browser/chromeos/power/peripheral_battery_observer_browsertest.cc',
       'browser/chromeos/preferences_browsertest.cc',
       'browser/chromeos/profiles/profile_helper_browsertest.cc',
       'browser/chromeos/shutdown_policy_browsertest.cc',
       'browser/chromeos/system/device_disabling_browsertest.cc',
       'browser/chromeos/system/tray_accessibility_browsertest.cc',
+      'browser/download/notification/download_notification_browsertest.cc',
       'browser/extensions/api/vpn_provider/vpn_provider_apitest.cc',
       'browser/ui/webui/options/chromeos/accounts_options_browsertest.cc',
       'browser/ui/webui/options/chromeos/guest_mode_options_ui_browsertest.cc',
       'browser/ui/webui/options/chromeos/shared_options_browsertest.cc',
     ],
     'chrome_browser_tests_policy_sources': [
       'browser/policy/cloud/cloud_policy_browsertest.cc',
       'browser/policy/cloud/cloud_policy_manager_browsertest.cc',
       'browser/policy/cloud/component_cloud_policy_browsertest.cc',
       'browser/policy/cloud/device_management_service_browsertest.cc',
@@ skipping 2468 matching lines @@
             ['enable_webrtc==1', {
               'dependencies': [
                 '../third_party/libjingle/libjingle.gyp:libjingle_webrtc'
               ]
             }],
           ],
         }]
     }],
   ],  # 'conditions'
 }