Add chrome/browser/extensions to "GN check"

ash/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/test.gni")
 import("//ui/base/ui_features.gni")
 
 assert(use_aura)
@@ skipping 97 matching lines @@
   if (is_chromeos) {
     deps += [
       "//chromeos",
       "//chromeos:power_manager_proto",
       "//components/quirks",
       "//device/bluetooth",
 
       # TODO(msw): Remove this; only ash_with_content should depend on webkit.
       "//third_party/WebKit/public:blink_headers",
       "//third_party/qcms",
-      "//ui/chromeos:ui_chromeos",
+      "//ui/chromeos",
       "//ui/chromeos/resources",
       "//ui/chromeos/strings",
       "//ui/display/util",
     ]
 
     data = [
       "display/test_data/",
     ]
   } else {
     sources -= [
@@ skipping 302 matching lines @@
   }
   if (is_chromeos) {
     sources += [ "first_run/first_run_helper_unittest.cc" ]
     deps += [
       "//chromeos",
       "//chromeos:power_manager_proto",
       "//chromeos:test_support_without_gmock",
       "//components/quirks",
       "//device/bluetooth",
       "//net:net",
-      "//ui/chromeos:ui_chromeos",
+      "//ui/chromeos",
       "//ui/display",
       "//ui/display:test_support",
       "//ui/display:test_util",
     ]
   } else {
     sources -= [
       "accelerators/magnifier_key_scroller_unittest.cc",
       "accelerators/spoken_feedback_toggler_unittest.cc",
       "display/resolution_notification_controller_unittest.cc",
       "touch/touchscreen_util_unittest.cc",
@@ skipping 36 matching lines @@
     configs += [ "//build/config/win:windowed" ]
     deps += [ "//sandbox" ]
   }
 
   if (is_chromeos) {
     deps += [ "//device/bluetooth" ]
   }
 }
 # When adding support for isolates, please have a look at run-time dependencies
 # in the ash_unittests_run target in ash.gyp.