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 f4d15b2eedadc3050bed99b495cc9f3bc1f32b17..5a799cd8e2f58751e12ad6a23331441b29e15c4b 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -1758,6 +1758,16 @@ PaintLayerScrollableArea::compositorAnimationTimeline() const {
   return nullptr;
 }
 
+void PaintLayerScrollableArea::getTickmarks(Vector<IntRect>& tickmarks) const {
+  if (!layer()->isRootLayer())
+    return;
+
+  // 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());