Make scrollAnimatorEnabled work on Mac like it does on other platforms

third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 23 matching lines @@
 namespace blink {
 
 class Pattern;
 
 class PLATFORM_EXPORT ScrollbarThemeMacCommon : public ScrollbarTheme {
 public:
     ~ScrollbarThemeMacCommon() override;
 
     void registerScrollbar(ScrollbarThemeClient&) override;
     void unregisterScrollbar(ScrollbarThemeClient&) override;
-    void preferencesChanged(float initialButtonDelay, float autoscrollButtonDelay, NSScrollerStyle preferredScrollerStyle, bool redraw, bool scrollAnimationEnabled, WebScrollbarButtonsPlacement);
+    void preferencesChanged(float initialButtonDelay, float autoscrollButtonDelay, NSScrollerStyle preferredScrollerStyle, bool redraw, WebScrollbarButtonsPlacement);
 
     bool supportsControlTints() const override { return true; }
 
     double initialAutoscrollTimerDelay() override;
     double autoscrollTimerDelay() override;
 
     void paintTickmarks(GraphicsContext&, const ScrollbarThemeClient&, const IntRect&) override;
 
     static NSScrollerStyle recommendedScrollerStyle();
 
@@ skipping 10 matching lines @@
     virtual void updateButtonPlacement(WebScrollbarButtonsPlacement) {}
 
     void paintGivenTickmarks(SkCanvas*, const ScrollbarThemeClient&, const IntRect&, const Vector<IntRect>&);
 
     RefPtr<Pattern> m_overhangPattern;
 };
 
 }
 
 #endif // ScrollbarThemeMacCommon_h