Disable scroll anchoring if the user engages in a drag motion

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 bca05f80462497b0b65e9db18734b68eed96ec62..0e44a3d6f7899531a339788b5a7dbf7868760c4d 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -622,6 +622,9 @@ public:
     // For PaintInvalidator temporarily. TODO(wangxianzhu): Move into PaintInvalidator.
     void invalidatePaintIfNeeded(const PaintInvalidationState&);
 
+    void setUserMayHaveDragged(bool dragged) override { m_userMayHaveDragged = dragged; }
+    bool userMayHaveDragged() const { return m_userMayHaveDragged; }
+
 protected:
     // Scroll the content via the compositor.
     bool scrollContentsFastPath(const IntSize& scrollDelta);
@@ -940,6 +943,8 @@ private:
         PaintInvalidationReason reason;
     };
     std::unique_ptr<Vector<ObjectPaintInvalidation>> m_trackedObjectPaintInvalidations;
+
+    bool m_userMayHaveDragged;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)