Make scrollAnimatorEnabled work on Mac like it does on other platforms

ui/gfx/gfx.gyp

 # Copyright (c) 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 95 matching lines @@
         'android/shared_device_display_info.h',
         'android/view_configuration.cc',
         'android/view_configuration.h',
         'animation/animation.cc',
         'animation/animation.h',
         'animation/animation_container.cc',
         'animation/animation_container.h',
         'animation/animation_container_element.h',
         'animation/animation_container_observer.h',
         'animation/animation_delegate.h',
+        'animation/animation_mac.mm',
+        'animation/animation_win.cc',
         'animation/linear_animation.cc',
         'animation/linear_animation.h',
         'animation/multi_animation.cc',
         'animation/multi_animation.h',
         'animation/slide_animation.cc',
         'animation/slide_animation.h',
         'animation/throb_animation.cc',
         'animation/throb_animation.h',
         'animation/tween.cc',
         'animation/tween.h',
@@ skipping 450 matching lines @@
          ],
          'variables': {
            'jni_gen_package': 'ui/gfx',
          },
          'includes': [ '../../build/jni_generator.gypi' ],
        },
      ],
     }],
   ],
 }