Make scrollAnimatorEnabled work on Mac like it does on other platforms

third_party/WebKit/public/web/mac/WebScrollbarTheme.h

Index: third_party/WebKit/public/web/mac/WebScrollbarTheme.h
diff --git a/third_party/WebKit/public/web/mac/WebScrollbarTheme.h b/third_party/WebKit/public/web/mac/WebScrollbarTheme.h
index a610ac935921d5ec23d74db123574d6daced444b..61385e8b4afc7a9719bd7ae018f0b4bce876bda2 100644
--- a/third_party/WebKit/public/web/mac/WebScrollbarTheme.h
+++ b/third_party/WebKit/public/web/mac/WebScrollbarTheme.h
@@ -49,12 +49,11 @@ public:
     // |autoscrollButtonDelay| is the current value of NSScrollerButtonPeriod from NSUserDefaults.
     // |preferredScrollerStyle| is the current value of +[NSScroller preferredScrollerStyle].
     // |redraw| is true if the update requires a redraw to include the change.
-    // |scrollAnimationEnabled| is the current value of NSScrollAnimationEnabled or AppleScrollAnimationEnabled from NSUserDefaults.
     // |buttonPlacement| is the current value of AppleScrollBarVariant
     BLINK_EXPORT static void updateScrollbarsWithNSDefaults(
         float initialButtonDelay, float autoscrollButtonDelay,
         ScrollerStyle preferredScrollerStyle, bool redraw,
-        bool scrollAnimationEnabled, WebScrollbarButtonsPlacement);
+        WebScrollbarButtonsPlacement);
 };
 
 } // namespace blink