Fix extension scrollbar regression bug, and add a regression test to

chrome/chrome_tests.gypi

 # Copyright 2013 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.
 {
   'includes': [
     'js_unittest_vars.gypi',
   ],
   'targets': [
     {
       'target_name': 'interactive_ui_tests',
@@ skipping 1432 matching lines @@
         'browser/ui/startup/startup_browser_creator_browsertest.cc',
         'browser/ui/sync/one_click_signin_bubble_links_delegate_browsertest.cc',
         'browser/ui/sync/profile_signin_confirmation_helper_browsertest.cc',
         'browser/ui/tab_modal_confirm_dialog_browsertest.cc',
         'browser/ui/tab_modal_confirm_dialog_browsertest.h',
         'browser/ui/toolbar/test_toolbar_model.cc',
         'browser/ui/toolbar/test_toolbar_model.h',
         'browser/ui/views/autofill/autofill_dialog_view_tester_views.cc',
         'browser/ui/views/autofill/autofill_dialog_view_tester_views.h',
         'browser/ui/views/autofill/autofill_popup_base_view_browsertest.cc',
+        'browser/ui/views/extensions/extension_install_dialog_view_browsertest.cc',
         'browser/ui/views/frame/browser_non_client_frame_view_ash_browsertest.cc',
         'browser/ui/views/frame/browser_view_browsertest.cc',
         'browser/ui/views/frame/browser_window_property_manager_browsertest_win.cc',
         'browser/ui/views/location_bar/zoom_bubble_view_browsertest.cc',
         'browser/ui/views/profiles/avatar_menu_button_browsertest.cc',
         'browser/ui/views/profiles/new_avatar_menu_button_browsertest.cc',
         'browser/ui/views/profiles/profile_chooser_view_browsertest.cc',
         'browser/ui/views/select_file_dialog_extension_browsertest.cc',
         'browser/ui/views/toolbar/browser_actions_container_browsertest.cc',
         'browser/ui/views/toolbar/toolbar_view_browsertest.cc',
@@ skipping 1538 matching lines @@
             ['enable_webrtc==1', {
               'dependencies': [
                 '../third_party/libjingle/libjingle.gyp:libjingle_webrtc'
               ]
             }],
           ],
         }]
     }],
   ],  # 'conditions'
 }