Fix Mac overlay scrollbars to show when programmatically scrolled.

third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm

Index: third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm
diff --git a/third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm b/third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm
index 6f940cb75decad84a1bb1ab2c93ed210adf89f45..3f9a198cfbbe9086ef3f90612be603a6d222d2eb 100644
--- a/third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm
+++ b/third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm
@@ -1040,14 +1040,8 @@ bool ScrollAnimatorMac::setScrollbarsVisibleForTesting(bool show)
 
 void ScrollAnimatorMac::cancelAnimation()
 {
+    [m_scrollAnimationHelper.get() _stopRun];
     m_haveScrolledSincePageLoad = false;
-
-    if (ScrollbarThemeMacCommon::isOverlayAPIAvailable()) {
-        if (scrollbarPaintTimerIsActive())
-            stopScrollbarPaintTimer();
-        [m_horizontalScrollbarPainterDelegate.get() cancelAnimations];
-        [m_verticalScrollbarPainterDelegate.get() cancelAnimations];
-    }
 }
 
 void ScrollAnimatorMac::handleWheelEventPhase(PlatformWheelEventPhase phase)