OverscrollGlow for mainThread-{BLINK CHANGES}

Source/core/page/EventHandler.h

Index: Source/core/page/EventHandler.h
diff --git a/Source/core/page/EventHandler.h b/Source/core/page/EventHandler.h
index eeb7df8c47208340f4bf9b8bb84a63aad03ad6f6..063113644d8d1887db4d7c80220bb10de037f3c1 100644
--- a/Source/core/page/EventHandler.h
+++ b/Source/core/page/EventHandler.h
@@ -125,6 +125,9 @@ public:
 
     void resizeScrollableAreaDestroyed();
 
+    FloatSize unusedDeltaForTesting() const { return m_unusedDelta; }
+    FloatSize accumulatedRootOverscrollForTesting() const { return m_accumulatedRootOverscroll; }
+
     IntPoint lastKnownMousePosition() const;
     Cursor currentMouseCursor() const { return m_currentMouseCursor; }
 
@@ -259,7 +262,7 @@ private:
     //            On output, if provided and a node was scrolled stopNode will point to that node.
     // delta - The delta to scroll by, in the units of the granularity parameter. (e.g. pixels, lines, pages, etc.)
     // absolutePoint - For wheel scrolls - the location, in absolute coordinates, where the event occured.
-    bool scroll(ScrollDirection, ScrollGranularity, Node* startNode = nullptr, Node** stopNode = nullptr, float delta = 1.0f, IntPoint absolutePoint = IntPoint());
+    ScrollResultOneDimensional scroll(ScrollDirection, ScrollGranularity, Node* startNode = nullptr, Node** stopNode = nullptr, float delta = 1.0f, IntPoint absolutePoint = IntPoint());
 
     void customizedScroll(const Node& startNode, ScrollState&);
 
@@ -374,6 +377,9 @@ private:
 
     LayoutSize m_offsetFromResizeCorner; // In the coords of m_resizeScrollableArea.
 
+    FloatSize m_unusedDelta;
+    FloatSize m_accumulatedRootOverscroll;
+
     bool m_mousePositionIsUnknown;
     IntPoint m_lastKnownMousePosition;
     IntPoint m_lastKnownMouseGlobalPosition;