Move constrained web dialog code back to chrome/.

ui/web_dialogs/web_dialogs.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': 'web_dialogs',
       'type': '<(component)',
       'dependencies': [
         '../../base/base.gyp:base',
         '../../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../../content/content.gyp:content_browser',
         '../../skia/skia.gyp:skia',
       ],
       'defines': [
         'WEB_DIALOGS_IMPLEMENTATION',
       ],
       'sources': [
         # All .cc, .h under web_dialogs, except unittests.
-        'constrained_web_dialog_ui.cc',
-        'constrained_web_dialog_ui.h',
         'web_dialog_delegate.cc',
         'web_dialog_delegate.h',
         'web_dialog_observer.h',
         'web_dialog_ui.cc',
         'web_dialog_ui.h',
         'web_dialog_web_contents_delegate.cc',
         'web_dialog_web_contents_delegate.h',
         'web_dialogs_export.h',
       ],
     },
   ],
 }