Make the UI an observer of downloads.

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 541 matching lines @@
         'browser/download/download_shelf_context_menu.cc',
         'browser/download/download_shelf_context_menu.h',
         'browser/download/download_started_animation.h',
         'browser/download/download_resource_throttle.cc',
         'browser/download/download_resource_throttle.h',
         'browser/download/download_status_updater.cc',
         'browser/download/download_status_updater.h',
         'browser/download/download_status_updater_gtk.cc',
         'browser/download/download_status_updater_mac.mm',
         'browser/download/download_status_updater_win.cc',
+        'browser/download/download_ui_controller.cc',
+        'browser/download/download_ui_controller.h',
         'browser/download/download_util.cc',
         'browser/download/download_util.h',
         'browser/download/all_download_item_notifier.cc',
         'browser/download/all_download_item_notifier.h',
         'browser/download/save_package_file_picker.cc',
         'browser/download/save_package_file_picker.h',
         'browser/download/save_package_file_picker_chromeos.cc',
         'browser/download/save_package_file_picker_chromeos.h',
         'browser/enumerate_modules_model_win.cc',
         'browser/enumerate_modules_model_win.h',
@@ skipping 2544 matching lines @@
             'proto_in_dir': '../third_party/cros_system_api/dbus',
             'proto_out_dir': 'chrome/browser/media_transfer_protocol',
           },
           'includes': ['../build/protoc.gypi'],
         },
       ],
      },
     ],
   ],
 }