[CSS Blending] Implement mix-blend-mode in software.

Source/core/rendering/RenderLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. 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@web.de>
@@ skipping 784 matching lines @@
     // but for now, we are always allocating it for RenderBox as it's safer.
     bool requiresScrollableArea() const { return renderBox(); }
     void updateScrollableArea();
 
     void updateResizerAreaSet();
     void updateScrollableAreaSet(bool hasOverflow);
 
     void dirtyAncestorChainVisibleDescendantStatus();
     void setAncestorChainHasVisibleDescendant();
 
+    void dirtyAncestorChainBlendedDescendantStatus();
+    void setAncestorChainBlendedDescendant();
+
     void updateDescendantDependentFlags();
 
     // This flag is computed by RenderLayerCompositor, which knows more about 3d hierarchies than we do.
     void setHas3DTransformedDescendant(bool b) { m_has3DTransformedDescendant = b; }
     bool has3DTransformedDescendant() const { return m_has3DTransformedDescendant; }
 
     void dirty3DTransformedDescendantStatus();
     // Both updates the status, and returns true if descendants of this have 3d.
     bool update3DTransformedDescendantStatus();
 
@@ skipping 78 matching lines @@
     // descendants in stacking order. This is one of the requirements of being
     // able to safely become a stacking context.
     unsigned m_canBePromotedToStackingContainer : 1;
     unsigned m_canBePromotedToStackingContainerDirty : 1;
 
     const unsigned m_isRootLayer : 1;
 
     unsigned m_usedTransparency : 1; // Tracks whether we need to close a transparent layer, i.e., whether
                                  // we ended up painting this layer or any descendants (and therefore need to
                                  // blend).
+    unsigned m_childLayerHasBlendMode : 1;
+    unsigned m_childLayerHasBlendModeStatusDirty : 1;
+
     unsigned m_paintingInsideReflection : 1; // A state bit tracking if we are painting inside a replica.
     unsigned m_repaintStatus : 2; // RepaintStatus
 
     unsigned m_visibleContentStatusDirty : 1;
     unsigned m_hasVisibleContent : 1;
     unsigned m_visibleDescendantStatusDirty : 1;
     unsigned m_hasVisibleDescendant : 1;
 
     unsigned m_isPaginated : 1; // If we think this layer is split by a multi-column ancestor, then this bit will be set.
 
@@ skipping 142 matching lines @@
 
 } // namespace WebCore
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const WebCore::RenderLayer*);
 void showLayerTree(const WebCore::RenderObject*);
 #endif
 
 #endif // RenderLayer_h