A11y: Add a browser test of TrayAccessibility.

chrome/chrome_tests.gypi

Index: chrome/chrome_tests.gypi
diff --git a/chrome/chrome_tests.gypi b/chrome/chrome_tests.gypi
index 81ce1d0970aeea2f517724e8553c7e89172487b1..b77f1c84d74b2313fb6e167ff135e806eff640ce 100644
--- a/chrome/chrome_tests.gypi
+++ b/chrome/chrome_tests.gypi
@@ -898,6 +898,7 @@
         'browser/chromeos/media/media_player_browsertest.cc',
         'browser/chromeos/memory/oom_priority_manager_browsertest.cc',
         'browser/chromeos/process_proxy/process_proxy_browsertest.cc',
+        'browser/chromeos/system/tray_accessibility_browsertest.cc',
         'browser/chromeos/ui/idle_logout_dialog_view_browsertest.cc',
         'browser/collected_cookies_browsertest.cc',
         'browser/content_settings/content_settings_browsertest.cc',
@@ -1489,6 +1490,7 @@
             # use_aura currently sets use_ash on Windows. So take these tests out
             # for win aura builds.
             # TODO: enable these for win_ash browser tests.
+            'browser/chromeos/system/tray_accessibility_browsertest.cc',
             'browser/ui/ash/chrome_shell_delegate_browsertest.cc',
             'browser/ui/ash/launcher/chrome_launcher_controller_browsertest.cc',
             'browser/ui/ash/launcher/launcher_favicon_loader_browsertest.cc',