Make scrollAnimatorEnabled work on Mac like it does on other platforms

ui/gfx/BUILD.gn

 # 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.
 
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
@@ skipping 24 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 724 matching lines @@
 if (is_android) {
   generate_jni("gfx_jni_headers") {
     sources = [
       "../android/java/src/org/chromium/ui/gfx/BitmapHelper.java",
       "../android/java/src/org/chromium/ui/gfx/DeviceDisplayInfo.java",
       "../android/java/src/org/chromium/ui/gfx/ViewConfigurationHelper.java",
     ]
     jni_package = "gfx"
   }
 }