MainFrame scrollbars should work with RFV instead of FV

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 725188f23942ca386bbefb1c7627b99b08560639..61022802eb52f9c1bfc03a6d46ae252399abd701 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -50,6 +50,7 @@
 #include "core/dom/Node.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/editing/FrameSelection.h"
+#include "core/editing/markers/DocumentMarkerController.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
@@ -1767,6 +1768,13 @@ PaintLayerScrollableArea::compositorAnimationTimeline() const {
   return nullptr;
 }
 
+void PaintLayerScrollableArea::getTickmarks(Vector<IntRect>& tickmarks) const {
+  // TODO(crbug.com/417782): Verify that tickmarks work with root layer
+  // scrolling.
+  if (LocalFrame* frame = box().frame())
+    frame->view()->getTickmarks(tickmarks);
+}
+
 PaintLayerScrollableArea*
 PaintLayerScrollableArea::ScrollbarManager::scrollableArea() {
   return toPaintLayerScrollableArea(m_scrollableArea.get());