Add a setting to do frame scrolls through the root layer.

Source/core/paint/BlockPainter.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BlockPainter_h
 #define BlockPainter_h
 
 namespace blink {
 
 struct PaintInfo;
 class InlineBox;
 class LayoutPoint;
 class LayoutRect;
 class RenderFlexibleBox;
 class RenderBlock;
 class RenderBox;
 class RenderObject;
 
 class BlockPainter {
 public:
     BlockPainter(RenderBlock& block) : m_renderBlock(block) { }
 
     void paint(PaintInfo&, const LayoutPoint& paintOffset);
     void paintObject(PaintInfo&, const LayoutPoint&);
     void paintChildren(PaintInfo&, const LayoutPoint&);
     void paintChildAsInlineBlock(RenderBox*, PaintInfo&, const LayoutPoint&);
+    void paintOverflowControlsIfNeeded(PaintInfo&, const LayoutPoint&);
 
     // inline-block elements paint all phases atomically. This function ensures that. Certain other elements
     // (grid items, flex items) require this behavior as well, and this function exists as a helper for them.
     // It is expected that the caller will call this function independent of the value of paintInfo.phase.
     static void paintAsInlineBlock(RenderObject*, PaintInfo&, const LayoutPoint&);
     static void paintChildrenOfFlexibleBox(RenderFlexibleBox&, PaintInfo&, const LayoutPoint& paintOffset);
     static void paintInlineBox(InlineBox&, PaintInfo&, const LayoutPoint& paintOffset);
 
 private:
     LayoutRect overflowRectForPaintRejection() const;
     bool hasCaret() const;
     void paintCarets(PaintInfo&, const LayoutPoint&);
     void paintContents(PaintInfo&, const LayoutPoint&);
     void paintColumnContents(PaintInfo&, const LayoutPoint&, bool paintFloats = false);
     void paintColumnRules(PaintInfo&, const LayoutPoint&);
     void paintChild(RenderBox*, PaintInfo&, const LayoutPoint&);
     void paintSelection(PaintInfo&, const LayoutPoint&);
     void paintContinuationOutlines(PaintInfo&, const LayoutPoint&);
 
     RenderBlock& m_renderBlock;
 };
 
 } // namespace blink
 
 #endif // BlockPainter_h