Reenables mash_wm_apptests

mojo/tools/data/apptests

Index: mojo/tools/data/apptests
diff --git a/mojo/tools/data/apptests b/mojo/tools/data/apptests
index 27b077a35baed300afe48e586f25a381ab2a0307..8c7c37f4fcdade0021fdf0cdf6aca948bec070ab 100644
--- a/mojo/tools/data/apptests
+++ b/mojo/tools/data/apptests
@@ -76,13 +76,12 @@ if config.target_os != config.OS_ANDROID:
       'test': 'mojo:mandoline_browser_apptests',
       'type': 'gtest_isolated',
     },
-    # TODO(sky): flakey, http://crbug.com/559412 .
-    # {
-    #   'test': 'mojo:mash_wm_apptests',
-    #   'type': 'gtest_isolated',
-    #   'args': ['--use-x11-test-config',
-    #            '--override-use-gl-with-osmesa-for-tests']
-    # },
+    {
+      'test': 'mojo:mash_wm_apptests',
+      'type': 'gtest_isolated',
+      'args': ['--use-x11-test-config',
+               '--override-use-gl-with-osmesa-for-tests']
+    },
     # TODO(xhwang): Fix and enable mojo:media_pipeline_integration_apptests.
     # http://crbug.com/501417
     {