Blink Support for Overlay Scrollbar Animation

Source/core/page/PageAnimator.cpp

Index: Source/core/page/PageAnimator.cpp
diff --git a/Source/core/page/PageAnimator.cpp b/Source/core/page/PageAnimator.cpp
index 8d97fe0a7015979101c4b5acd34da689df20c17c..c988473dc0af8c7c1e365fe5072b5b53b6d1a355 100644
--- a/Source/core/page/PageAnimator.cpp
+++ b/Source/core/page/PageAnimator.cpp
@@ -53,8 +53,13 @@ void PageAnimator::serviceScriptedAnimations(double monotonicAnimationStartTime)
         SVGDocumentExtensions::serviceOnAnimationFrame(*documents[i], monotonicAnimationStartTime);
     }
 
-    for (size_t i = 0; i < documents.size(); ++i)
+    for (size_t i = 0; i < documents.size(); ++i) {
         documents[i]->serviceScriptedAnimations(monotonicAnimationStartTime);
+        if (const FrameView::ScrollableAreaSet* scrollableAreas = documents[i]->view()->scrollableAreas()) {
+            for (FrameView::ScrollableAreaSet::iterator it = scrollableAreas->begin(); it != scrollableAreas->end(); ++it)
+                (*it)->serviceScrollbarAnimations();
+        }
+    }
 }
 
 void PageAnimator::scheduleVisualUpdate()