Introduce a helper for OPENFILENAME struct to make certain logic testable.

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 334 matching lines @@
         'win/hwnd_subclass.cc',
         'win/hwnd_subclass.h',
         'win/internal_constants.cc',
         'win/internal_constants.h',
         'win/lock_state.cc',
         'win/lock_state.h',
         'win/message_box_win.cc',
         'win/message_box_win.h',
         'win/mouse_wheel_util.cc',
         'win/mouse_wheel_util.h',
+        'win/open_file_name_win.cc',
+        'win/open_file_name_win.h',
         'win/scoped_ole_initializer.cc',
         'win/scoped_ole_initializer.h',
         'win/shell.cc',
         'win/shell.h',
         'win/touch_input.cc',
         'win/touch_input.h',
         'win/window_event_target.cc',
         'win/window_event_target.h',
         'window_open_disposition.cc',
         'window_open_disposition.h',
@@ skipping 382 matching lines @@
            ],
            'variables': {
              'jni_gen_package': 'ui',
            },
            'includes': [ '../../build/jni_generator.gypi' ],
          },
        ],
     }],
   ],
 }