Make scrollAnimatorEnabled work on Mac like it does on other platforms

ui/gfx/animation/animation.cc

Index: ui/gfx/animation/animation.cc
diff --git a/ui/gfx/animation/animation.cc b/ui/gfx/animation/animation.cc
index 3c298285e1310ea4d1b9b0e2c5fc5afed193af2e..5e97b9365514481f4fde2516e8e265c0ef757671 100644
--- a/ui/gfx/animation/animation.cc
+++ b/ui/gfx/animation/animation.cc
@@ -14,6 +14,10 @@
 #include "base/win/windows_version.h"
 #endif
 
+#if defined(OS_MACOSX)
+#include "base/mac/mac_util.h"
+#endif
+
 namespace gfx {
 
 Animation::Animation(base::TimeDelta timer_interval)
@@ -108,6 +112,17 @@ bool Animation::ShouldRenderRichAnimation() {
 #endif
 }
 
+// static
+bool Animation::ScrollAnimationsEnabledBySystem() {
+#if defined(OS_WIN)
+  return ShouldRenderRichAnimation();
+#elif defined(OS_MACOSX)
+  return base::mac::IsScrollAnimationEnabled();
+#else
+  return true;
+#endif
+}
+
 bool Animation::ShouldSendCanceledFromStop() {
   return false;
 }