[Mac] Move UI item validation to UserInterfaceItemCommandHandler.

ui/base/ui_base.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 113 matching lines @@
         'cocoa/remote_layer_api.h',
         'cocoa/remote_layer_api.mm',
         'cocoa/three_part_image.h',
         'cocoa/three_part_image.mm',
         'cocoa/tool_tip_base_view.h',
         'cocoa/tool_tip_base_view.mm',
         'cocoa/tracking_area.h',
         'cocoa/tracking_area.mm',
         'cocoa/underlay_opengl_hosting_window.h',
         'cocoa/underlay_opengl_hosting_window.mm',
+        'cocoa/user_interface_item_command_handler.h',
         'cocoa/view_description.h',
         'cocoa/view_description.mm',
         'cocoa/window_size_constants.h',
         'cocoa/window_size_constants.mm',
         'cursor/cursor.cc',
         'cursor/cursor.h',
         'cursor/cursor_android.cc',
         'cursor/cursor_loader.h',
         'cursor/cursor_loader_android.cc',
         'cursor/cursor_loader_ozone.cc',
@@ skipping 575 matching lines @@
            ],
            'variables': {
              'jni_gen_package': 'ui',
            },
            'includes': [ '../../build/jni_generator.gypi' ],
          },
        ],
     }],
   ],
 }