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 561 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 2561 matching lines @@
             'package_name': 'org/chromium/chrome/browser/ui/toolbar',
             'template_deps': ['browser/ui/toolbar/toolbar_model_security_level_list.h'],
           },
           'includes': [ '../build/android/java_cpp_template.gypi' ],
         },
       ],
      },
     ],
   ],
 }