Mac: Don't repaint scrollbars every frame

cc/cc_tests.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,
     'cc_unit_tests_source_files': [
       'animation/animation_host_unittest.cc',
       'animation/animation_player_unittest.cc',
@@ skipping 32 matching lines @@
       'layers/io_surface_layer_impl_unittest.cc',
       'layers/layer_impl_unittest.cc',
       'layers/layer_iterator_unittest.cc',
       'layers/layer_position_constraint_unittest.cc',
       'layers/layer_proto_converter_unittest.cc',
       'layers/layer_unittest.cc',
       'layers/layer_utils_unittest.cc',
       'layers/nine_patch_layer_impl_unittest.cc',
       'layers/nine_patch_layer_unittest.cc',
       'layers/painted_scrollbar_layer_impl_unittest.cc',
+      'layers/painted_scrollbar_layer_unittest.cc',
       'layers/picture_image_layer_impl_unittest.cc',
       'layers/picture_image_layer_unittest.cc',
       'layers/picture_layer_impl_unittest.cc',
       'layers/picture_layer_unittest.cc',
       'layers/render_surface_impl_unittest.cc',
       'layers/render_surface_unittest.cc',
       'layers/scrollbar_layer_unittest.cc',
       'layers/solid_color_layer_impl_unittest.cc',
       'layers/solid_color_scrollbar_layer_impl_unittest.cc',
       'layers/surface_layer_impl_unittest.cc',
@@ skipping 402 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }