Skip gl surface init when headless; enable wm apptests.

mojo/tools/data/apptests

 # This file contains a list of Mojo gtest unit tests.
 #
 # This must be valid Python. It may use the |config| global that will be a
 # mopy.config.Config object, and must set a |tests| global that will contain the
 # list of tests to run.
 #
 # The entries in |tests| are dictionaries of the following form:
 #   {
 #     # Required URL for apptest.
 #     "test": "mojo:test_app_url",
@@ skipping 26 matching lines @@
   },
   # TODO(msw|jam): Fix and enable the shell_apptests: http://crbug.com/479316
   #{
   #  "test": "mojo:shell_apptests",
   #},
   {
     "test": "mojo:view_manager_apptests",
     "type": "gtest_isolated",
     "shell-args": ["--url-mappings=mojo:window_manager=mojo:test_window_manager"]
   },
-  # TODO(msw): Fix and enable window_manager_apptests: http://crbug.com/480040
-  #{
-  #  "test": "mojo:window_manager_apptests",
-  #  "shell-args": ["--use-test-config", "--use-headless-config"]
-  #},
+  {
+    "test": "mojo:window_manager_apptests",
+    "shell-args": ["--use-headless-config"]
+  },
 ]