MainFrame scrollbars should work with RFV instead of FV

third_party/WebKit/Source/core/frame/RootFrameViewport.h

Index: third_party/WebKit/Source/core/frame/RootFrameViewport.h
diff --git a/third_party/WebKit/Source/core/frame/RootFrameViewport.h b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
index 93e554d80a95318c2f1f04990b88476a668d2843..729ec726bc016c5af7b027c561179b98d23c88c7 100644
--- a/third_party/WebKit/Source/core/frame/RootFrameViewport.h
+++ b/third_party/WebKit/Source/core/frame/RootFrameViewport.h
@@ -64,11 +64,6 @@ class CORE_EXPORT RootFrameViewport final
   IntRect visibleContentRect(
       IncludeScrollbarsInRect = ExcludeScrollbars) const override;
   bool shouldUseIntegerScrollOffset() const override;
-  LayoutRect visualRectForScrollbarParts() const override {
-    ASSERT_NOT_REACHED();
-    return LayoutRect();
-  }
-  bool isActive() const override;
   int scrollSize(ScrollbarOrientation) const override;
   bool isScrollCornerVisible() const override;
   IntRect scrollCornerRect() const override;
@@ -107,6 +102,34 @@ class CORE_EXPORT RootFrameViewport final
                                       const LayoutObject*,
                                       unsigned = 0) const final;
 
+  // Scrollbar related
+  // TODO(crbug.com/661236): Seperate the scrollbar related logic from
+  // ScrollableArea.
+  Scrollbar* horizontalScrollbar() const override;
+  Scrollbar* verticalScrollbar() const override;
+  bool isActive() const override;
+  bool hasOverlayScrollbars() const override;
+  void setScrollbarNeedsPaintInvalidation(ScrollbarOrientation) override;
+  LayoutRect visualRectForScrollbarParts() const override;
+  ScrollbarOverlayColorTheme getScrollbarOverlayColorTheme() const override;
+  void getTickmarks(Vector<IntRect>& rects) const override;
+  void mouseEnteredScrollbar(Scrollbar&) override;
+  void mouseExitedScrollbar(Scrollbar&) override;
+  void scrollbarVisibilityChanged() override;
+  bool scrollbarsHidden() const override;
+  IntRect convertFromScrollbarToContainingWidget(const Scrollbar&,
+                                                 const IntRect&) const override;
+  IntRect convertFromContainingWidgetToScrollbar(const Scrollbar&,
+                                                 const IntRect&) const override;
+  IntPoint convertFromScrollbarToContainingWidget(
+      const Scrollbar&,
+      const IntPoint&) const override;
+  IntPoint convertFromContainingWidgetToScrollbar(
+      const Scrollbar&,
+      const IntPoint&) const override;
+  ScrollOffset scrollAnimatorDesiredTargetOffset() const override;
+  void setScrollCornerNeedsPaintInvalidation() override;
+
  private:
   RootFrameViewport(ScrollableArea& visualViewport,
                     ScrollableArea& layoutViewport);