Convert Settings::rootLayerScrolls to RuntimeEnabledFeatures

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 811 matching lines @@
     return overflow == OverflowAuto || overflow == OverflowOverlay;
 }
 
 // This function returns true if the given box requires overflow scrollbars (as
 // opposed to the 'viewport' scrollbars managed by the PaintLayerCompositor).
 // FIXME: we should use the same scrolling machinery for both the viewport and
 // overflow. Currently, we need to avoid producing scrollbars here if they'll be
 // handled externally in the RLC.
 static bool canHaveOverflowScrollbars(const LayoutBox& box)
 {
-    bool rootLayerScrolls = box.document().settings() && box.document().settings()->rootLayerScrolls();
-    return (rootLayerScrolls || !box.isLayoutView()) && box.document().viewportDefiningElement() != box.node();
+    return (RuntimeEnabledFeatures::rootLayerScrollingEnabled() || !box.isLayoutView()) && box.document().viewportDefiningElement() != box.node();
 }
 
 void PaintLayerScrollableArea::updateAfterStyleChange(const ComputedStyle* oldStyle)
 {
     // Don't do this on first style recalc, before layout has ever happened.
     if (!overflowRect().size().isZero())
         updateScrollableAreaSet(hasScrollableHorizontalOverflow() || hasScrollableVerticalOverflow());
 
     if (!canHaveOverflowScrollbars(box()))
         return;
@@ skipping 928 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollPositionClampScope::clampScrollableAreas()
 {
     for (auto& scrollableArea : *s_needsClamp)
         scrollableArea->clampScrollPositionsAfterLayout();
     delete s_needsClamp;
     s_needsClamp = nullptr;
 }
 
 } // namespace blink