Switch mash_browser_tests to Ozone X11 platform.

testing/buildbot/gn_isolate_map.pyl

 ## Copyright 2015 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.
 
 # This is a .pyl, or "Python Literal", file. You can treat it just like a
 # .json file, with the following exceptions:
 # * all keys must be quoted (use single quotes, please);
 # * comments are allowed, using '#' syntax; and
 # * trailing commas are allowed.
 
@@ skipping 549 matching lines @@
     "type": "console_test_launcher",
   },
   "mac_installer_unittests": {
     "label": "//chrome/installer/mac/app:mac_installer_unittests",
     "type": "console_test_launcher",
   },
   "mash:all" : {
     "label": "//mash:all",
     "type": "additional_compile_target",
   },
+  "mash_browser_tests": {
+    "label": "//chrome/test:mash_browser_tests",
+    "label_type": "group",
+    "type": "windowed_test_launcher",
+    "executable": "browser_tests",
+    "args": [
+      "--run-in-mash",
+      "--use-test-config",
+      "--service-overrides=../../chrome/app/mash/mash_service_overrides.json",
+    ],
+  },
   "media_unittests": {
     "label": "//media:media_unittests",
     "type": "windowed_test_launcher",
   },
   "media_service_unittests": {
     "label": "//media/mojo/services:media_service_unittests",
     "type": "console_test_launcher",
   },
   "media_blink_unittests": {
     "label": "//media/blink:media_blink_unittests",
@@ skipping 427 matching lines @@
   },
   "wm_unittests": {
     "label": "//ui/wm:wm_unittests",
     "type": "windowed_test_launcher",
   },
   "wtf_unittests": {
     "label": "//third_party/WebKit/Source/wtf:wtf_unittests",
     "type": "console_test_launcher",
   },
 }