Allow OSExchangeData::Provider to be overridden at run time.

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 224 matching lines @@
         'dragdrop/drop_target_event.cc',
         'dragdrop/drop_target_event.h',
         'dragdrop/drop_target_win.cc',
         'dragdrop/drop_target_win.h',
         'dragdrop/file_info.cc',
         'dragdrop/file_info.h',
         'dragdrop/os_exchange_data.cc',
         'dragdrop/os_exchange_data.h',
         'dragdrop/os_exchange_data_provider_aura.cc',
         'dragdrop/os_exchange_data_provider_aura.h',
+        'dragdrop/os_exchange_data_provider_builder_mac.h',
+        'dragdrop/os_exchange_data_provider_builder_mac.mm',
         'dragdrop/os_exchange_data_provider_aurax11.cc',
         'dragdrop/os_exchange_data_provider_aurax11.h',
+        'dragdrop/os_exchange_data_provider_factory.cc',
+        'dragdrop/os_exchange_data_provider_factory.h',
         'dragdrop/os_exchange_data_provider_mac.h',
         'dragdrop/os_exchange_data_provider_mac.mm',
         'dragdrop/os_exchange_data_provider_win.cc',
         'dragdrop/os_exchange_data_provider_win.h',
         'hit_test.h',
         'idle/idle.cc',
         'idle/idle.h',
         'idle/idle_android.cc',
         'idle/idle_chromeos.cc',
         'idle/idle_linux.cc',
@@ skipping 348 matching lines @@
             '../../build/linux/system.gyp:xscrnsaver',
           ],
         }],
         ['toolkit_views==0', {
           'sources!': [
             'dragdrop/drag_drop_types.h',
             'dragdrop/drop_target_event.cc',
             'dragdrop/drop_target_event.h',
             'dragdrop/os_exchange_data.cc',
             'dragdrop/os_exchange_data.h',
+            'dragdrop/os_exchange_data_provider_factory.cc',
+            'dragdrop/os_exchange_data_provider_factory.h',
             'nine_image_painter_factory.cc',
             'nine_image_painter_factory.h',
           ],
         }],
         ['OS=="android"', {
           'sources!': [
             'cursor/image_cursors.cc',
             'cursor/image_cursors.h',
             'default_theme_provider.cc',
             'dragdrop/drag_utils.cc',
@@ skipping 144 matching lines @@
            ],
            'variables': {
              'jni_gen_package': 'ui',
            },
            'includes': [ '../../build/jni_generator.gypi' ],
          },
        ],
     }],
   ],
 }