Mac: Optimize TabView drawing.

ui/base/ui_base.gyp

 # Copyright 2014 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,
   },
   'targets': [
     {
@@ skipping 105 matching lines @@
         'cocoa/menu_controller.h',
         'cocoa/menu_controller.mm',
         'cocoa/nib_loading.h',
         'cocoa/nib_loading.mm',
         'cocoa/nsgraphics_context_additions.h',
         'cocoa/nsgraphics_context_additions.mm',
         'cocoa/nsview_additions.h',
         'cocoa/nsview_additions.mm',
         'cocoa/remote_layer_api.h',
         'cocoa/remote_layer_api.mm',
+        'cocoa/three_part_image.h',
+        'cocoa/three_part_image.mm',
         'cocoa/tracking_area.h',
         'cocoa/tracking_area.mm',
         'cocoa/underlay_opengl_hosting_window.h',
         'cocoa/underlay_opengl_hosting_window.mm',
         'cocoa/view_description.h',
         'cocoa/view_description.mm',
         'cocoa/window_size_constants.h',
         'cocoa/window_size_constants.mm',
         'cursor/cursor.cc',
         'cursor/cursor.h',
@@ skipping 568 matching lines @@
            ],
            'variables': {
              'jni_gen_package': 'ui',
            },
            'includes': [ '../../build/jni_generator.gypi' ],
          },
        ],
     }],
   ],
 }