Reenable maps_pixel_test including in gatekeeper.

scripts/slave/gatekeeper.json

 {
   "comment": ["This is a configuration file for gatekeeper_ng.py",
               "Look at that for documentation on this file's format."],
 
   "masters": {
     "https://build.chromium.org/p/chromium": [
       {
         "categories": [
           "chromium_archive_build",
           "chromium_checkdeps",
@@ skipping 97 matching lines @@
           "GPU Mac Builder (dbg)",
           "GPU Win Builder (dbg)",
           "Linux Debug (NVIDIA)",
           "Mac 10.8 Debug (Intel)",
           "Mac Debug (Intel)",
           "Mac Retina Debug",
           "Win7 Debug (NVIDIA)",
           "Win8 Debug (NVIDIA)"
         ],
         "comment": [
-          "Re-enable maps_pixel_test once crbug.com/395914 is resolved."
+          "Any steps whose results must be temporarily ignored (e.g.",
+          "due to flakiness) can be added here."
         ],
         "excluded_steps": [
-          "maps_pixel_test"
         ]
       }
     ],
     "https://build.chromium.org/p/chromium.linux": [
       {
         "categories": [
           "chromium_tree_closer",
           "chromium_recipes"
         ],
         "builders": {
@@ skipping 341 matching lines @@
         "sandbox_linux_unittests",
         "sql_unittests",
         "sync_unit_tests",
         "ui_unittests",
         "unit_tests",
         "url_unittests"
       ]
     }
   }
 }