Giving focus to an app shim brings windows belonging to that app to the foreground.

ui/ui.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'includes': [
     'shell_dialogs.gypi',
@@ skipping 77 matching lines @@
         'base/clipboard/custom_data_helper_x.cc',
         'base/clipboard/scoped_clipboard_writer.cc',
         'base/clipboard/scoped_clipboard_writer.h',
         'base/cocoa/base_view.h',
         'base/cocoa/base_view.mm',
         'base/cocoa/events_mac.mm',
         'base/cocoa/find_pasteboard.h',
         'base/cocoa/find_pasteboard.mm',
         'base/cocoa/focus_tracker.h',
         'base/cocoa/focus_tracker.mm',
+        'base/cocoa/focus_window_set.h',
+        'base/cocoa/focus_window_set.mm',
         'base/cocoa/fullscreen_window_manager.h',
         'base/cocoa/fullscreen_window_manager.mm',
         'base/cocoa/nib_loading.h',
         'base/cocoa/nib_loading.mm',
         'base/cocoa/tracking_area.h',
         'base/cocoa/tracking_area.mm',
         'base/cocoa/underlay_opengl_hosting_window.h',
         'base/cocoa/underlay_opengl_hosting_window.mm',
         'base/cocoa/window_size_constants.h',
         'base/cocoa/window_size_constants.mm',
@@ skipping 829 matching lines @@
           'link_settings': {
             'libraries': [
               '$(SDKROOT)/System/Library/Frameworks/Cocoa.framework',
             ],
           },
         },
       ],
     }],
   ],
 }