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

printing/printing.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,
   },
   'targets': [
     {
       'target_name': 'printing',
       'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_i18n',
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../skia/skia.gyp:skia',
         '../third_party/icu/icu.gyp:icui18n',
         '../third_party/icu/icu.gyp:icuuc',
         '../ui/gfx/gfx.gyp:gfx',
-        '../ui/ui.gyp:shell_dialogs',
+        '../ui/shell_dialogs/shell_dialogs.gyp:shell_dialogs',
         '../ui/ui.gyp:ui',
         '../url/url.gyp:url_lib',
       ],
       'defines': [
         'PRINTING_IMPLEMENTATION',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
@@ skipping 296 matching lines @@
                   '<!@(python cups_config_helper.py --cflags)',
                 ],
               }],
             ],
           },
         }],
       ],
     },
   ],
 }