Conditionally create PaintLayer's scrollable area object

third_party/WebKit/Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 985 matching lines @@
         m_mediaForPositionNotification.remove(at);
 }
 
 void LayoutView::sendMediaPositionChangeNotifications(const IntRect& visibleRect)
 {
     for (auto& media : m_mediaForPositionNotification) {
         media->notifyPositionMayHaveChanged(visibleRect);
     }
 }
 
+void LayoutView::updateFromStyle()
+{
+    LayoutBlockFlow::updateFromStyle();
+
+    // LayoutView of the main frame is responsible for painting base background.
+    if (!document().ownerElement())
+        setHasBoxDecorationBackground(true);
+}
+
+bool LayoutView::allowsOverflowClip() const
+{
+    return document().settings() && document().settings()->rootLayerScrolls();
+}
+
 } // namespace blink