Move the test template to //testing/test.gni (part 2)

ui/message_center/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
+import("//testing/rules.gni")
 
 component("message_center") {
   deps = [
     "//base",
     "//base:i18n",
     "//base/third_party/dynamic_annotations",
     "//skia",
     "//ui/accessibility",
     "//ui/base",
     "//ui/events",
@@ skipping 210 matching lines @@
       deps += [
         # Compositor is needed by message_center_view_unittest.cc and for the
         # fonts used by bounded_label_unittest.cc.
         "//ui/compositor",
         "//ui/views",
         "//ui/views:test_support",
       ]
     }
   }  # enable_notifications && !is_android
 }