Make all gesture scrolls use customization path internally

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

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index 158e3e8d680ef1455eb9343f2c7ba4697a7529db..f47f90e6ff530ea8613841052f1701d3b9347d51 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -480,8 +480,12 @@ Document::Document(const DocumentInit& initializer, DocumentClassFlags documentC
     ViewportScrollCallback* applyScroll = nullptr;
     if (isInMainFrame()) {
         applyScroll = RootScrollerController::createViewportApplyScroll(
-            frameHost()->topControls(), frameHost()->overscrollController());
+            &frameHost()->topControls(), &frameHost()->overscrollController());
+    } else {
+        applyScroll =
+            RootScrollerController::createViewportApplyScroll(nullptr, nullptr);
     }
+
     m_rootScrollerController =
         RootScrollerController::create(*this, applyScroll);
 
@@ -618,9 +622,9 @@ Element* Document::rootScroller() const
     return m_rootScrollerController->get();
 }
 
-bool Document::isEffectiveRootScroller(const Element& element) const
+Element* Document::effectiveRootScroller() const
 {
-    return m_rootScrollerController->effectiveRootScroller() == element;
+    return m_rootScrollerController->effectiveRootScroller();
 }
 
 bool Document::isInMainFrame() const