Improve scroll anchoring's interactions with the visual viewport

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

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index 808842b6a230e10ecdc9957f052749fff421139c..e9c1059f1eb30ce1f643cb8f72b2e36ab0e03bce 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -393,6 +393,7 @@ public:
     bool shouldPlaceVerticalScrollbarOnLeft() const override;
     Widget* getWidget() override;
     CompositorAnimationTimeline* compositorAnimationTimeline() const override;
+    LayoutBox* layoutBox() const override { return layoutView(); }
 
     LayoutRect scrollIntoView(
         const LayoutRect& rectInContent,
@@ -606,6 +607,7 @@ public:
     FloatSize viewportSizeForViewportUnits() const;
 
     ScrollAnchor& scrollAnchor() { return m_scrollAnchor; }
+    void clearScrollAnchor();
 
     // For PaintInvalidator temporarily. TODO(wangxianzhu): Move into PaintInvalidator.
     void invalidatePaintIfNeeded(const PaintInvalidationState&);