Cleanup and refactor RootScrollerController.

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 5ff62967e326ce3888314c78ce9357148d38ec0d..bb41789bc6f4c811ba5c9124585cdd6e46d7ff98 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -534,7 +534,7 @@ void Element::callDistributeScroll(ScrollState& scrollState)
     // allow the viewport scroll callback so we don't disable overscroll.
     // crbug.com/623079.
     bool disableCustomCallbacks = !scrollState.isDirectManipulation()
-        && !document().isViewportScrollCallback(callback);
+        && !document().rootScrollerController()->isViewportScrollCallback(callback);
 
     if (!callback || disableCustomCallbacks) {
         nativeDistributeScroll(scrollState);
@@ -612,7 +612,7 @@ void Element::callApplyScroll(ScrollState& scrollState)
     // allow the viewport scroll callback so we don't disable overscroll.
     // crbug.com/623079.
     bool disableCustomCallbacks = !scrollState.isDirectManipulation()
-        && !document().isViewportScrollCallback(callback);
+        && !document().rootScrollerController()->isViewportScrollCallback(callback);
 
     if (!callback || disableCustomCallbacks) {
         nativeApplyScroll(scrollState);