Add tests for Headless Linux bot

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.
 
 # gn_isolate_map.pyl - A mapping of Ninja build target names to GN labels and
 # test type classifications for the tests that are run on the bots.
 #
 # This mapping is used by MB so that we can uniformly refer to test binaries
 # by their Ninja target names in the recipes and not need to worry about how
 # they are referred to in GN or GYP specifically (the GYP target name is pretty
@@ skipping 277 matching lines @@
     "args": [],
   },
   "google_apis_unittests": {
     "label": "//google_apis:google_apis_unittests",
     "type": "console_test_launcher",
   },
   "gpu_unittests": {
     "label": "//gpu:gpu_unittests",
     "type": "windowed_test_launcher",
   },
+  "headless_browsertests": {
+    "label": "//headless:headless_browsertests",
+    "type": "console_test_launcher",
+  },
   "installer_util_unittests": {
     "label": "//chrome/installer/util:installer_util_unittests",
     "type": "console_test_launcher",
   },
   "interactive_ui_tests": {
     "label": "//chrome/test:interactive_ui_tests",
     "type": "windowed_test_launcher",
   },
   "ipc_mojo_unittests": {
     "label": "//ipc/mojo:ipc_mojo_unittests",
@@ skipping 261 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",
   },
 }