Initial scroll-blocks-on compositor integration

Source/core/rendering/RenderBox.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007 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.
  *
@@ skipping 58 matching lines @@
     LayoutUnit m_overrideLogicalContentWidth;
 
     // Set by RenderBox::updatePreviousBorderBoxSizeIfNeeded().
     LayoutSize m_previousBorderBoxSize;
 };
 
 class RenderBox : public RenderBoxModelObject {
 public:
     explicit RenderBox(ContainerNode*);
 
-    // hasAutoZIndex only returns true if the element is positioned or a flex-item since
-    // position:static elements that are not flex-items get their z-index coerced to auto.
-    virtual LayerType layerTypeRequired() const override
-    {
-        if (isPositioned() || createsGroup() || hasClipPath() || hasTransformRelatedProperty() || hasHiddenBackface() || hasReflection() || style()->specifiesColumns() || !style()->hasAutoZIndex() || style()->shouldCompositeForCurrentAnimations())
-            return NormalLayer;
-        if (hasOverflowClip())
-            return OverflowClipLayer;
-
-        return NoLayer;
-    }
+    virtual LayerType layerTypeRequired() const override;
 
     virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;
 
     virtual bool backgroundShouldAlwaysBeClipped() const { return false; }
 
     // Use this with caution! No type checking is done!
     RenderBox* firstChildBox() const;
     RenderBox* lastChildBox() const;
 
     int pixelSnappedWidth() const { return m_frameRect.pixelSnappedWidth(); }
@@ skipping 751 matching lines @@
         if (UNLIKELY(inlineBoxWrapper() != 0))
             deleteLineBoxWrapper();
     }
 
     ensureRareData().m_inlineBoxWrapper = boxWrapper;
 }
 
 } // namespace blink
 
 #endif // RenderBox_h