ui: Have shell_dialogs into its own gyp file under its shell_dialogs/ directory.

ash/ash.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
     'grit_out_dir': '<(SHARED_INTERMEDIATE_DIR)/chrome',
   },
   'includes': [
@@ skipping 689 matching lines @@
         '../ui/aura/aura.gyp:aura',
         '../ui/aura/aura.gyp:aura_test_support',
         '../ui/compositor/compositor.gyp:compositor',
         '../ui/events/events.gyp:events',
         '../ui/gfx/gfx.gyp:gfx',
         '../ui/keyboard/keyboard.gyp:keyboard',
         '../ui/message_center/message_center.gyp:message_center',
         '../ui/message_center/message_center.gyp:message_center_test_support',
         '../ui/ui.gyp:ui',
         '../ui/ui.gyp:ui_resources',
-        '../ui/ui.gyp:ui_test_support',
+        '../ui/ui_unittests.gyp:ui_test_support',
         '../ui/views/views.gyp:views',
         '../ui/views/views.gyp:views_examples_with_content_lib',
         '../ui/views/views.gyp:views_test_support',
         '../ui/views/views.gyp:views_with_content_test_support',
         '../ui/web_dialogs/web_dialogs.gyp:web_dialogs_test_support',
         '../url/url.gyp:url_lib',
         'ash_strings.gyp:ash_strings',
         'ash',
         'ash_resources',
         'ash_test_support',
@@ skipping 234 matching lines @@
             },
           },
           'dependencies': [
             '../sandbox/sandbox.gyp:sandbox',
           ],
         }],
       ],
     },
   ],
 }