Add a first-class off-store install UI to chrome://extensions/.

chrome/chrome_browser.gypi

 # Copyright (c) 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 3634 matching lines @@
         'browser/ui/webui/downloads_ui.cc',
         'browser/ui/webui/downloads_ui.h',
         'browser/ui/webui/extensions/extension_activity_ui.cc',
         'browser/ui/webui/extensions/extension_activity_ui.h',
         'browser/ui/webui/extensions/extension_icon_source.cc',
         'browser/ui/webui/extensions/extension_icon_source.h',
         'browser/ui/webui/extensions/extension_settings_handler.cc',
         'browser/ui/webui/extensions/extension_settings_handler.h',
         'browser/ui/webui/extensions/extensions_ui.cc',
         'browser/ui/webui/extensions/extensions_ui.h',
+        'browser/ui/webui/extensions/install_extension_handler.cc',
+        'browser/ui/webui/extensions/install_extension_handler.h',
         'browser/ui/webui/extensions/pack_extension_handler.cc',
         'browser/ui/webui/extensions/pack_extension_handler.h',
         'browser/ui/webui/favicon_source.cc',
         'browser/ui/webui/favicon_source.h',
         'browser/ui/webui/fileicon_source.cc',
         'browser/ui/webui/fileicon_source.h',
         'browser/ui/webui/flags_ui.cc',
         'browser/ui/webui/flags_ui.h',
         'browser/ui/webui/flash_ui.cc',
         'browser/ui/webui/flash_ui.h',
@@ skipping 1586 matching lines @@
       'type': 'static_library',
       'sources': [ 'browser/chromeos/gdata/gdata.proto' ],
       'variables': {
         'proto_in_dir': 'browser/chromeos/gdata',
         'proto_out_dir': 'chrome/browser/chromeos/gdata',
       },
       'includes': [ '../build/protoc.gypi' ]
     },
   ],
 }