Compute style-determined compositing reasons during recalc style

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 605 matching lines @@
 
     bool hasNonCompositedChild() const { return m_compositingProperties.hasNonCompositedChild; }
     void setHasNonCompositedChild(bool b)  { m_compositingProperties.hasNonCompositedChild = b; }
 
     bool shouldIsolateCompositedDescendants() const { return m_compositingProperties.shouldIsolateCompositedDescendants; }
     void setShouldIsolateCompositedDescendants(bool b)  { m_compositingProperties.shouldIsolateCompositedDescendants = b; }
 
     bool lostGroupedMapping() const { return m_compositingProperties.lostGroupedMapping; }
     void setLostGroupedMapping(bool b) { m_compositingProperties.lostGroupedMapping = b; }
 
-    void setCompositingReasons(CompositingReasons);
+    void setCompositingReasons(CompositingReasons, CompositingReasons mask = CompositingReasonAll);
     CompositingReasons compositingReasons() const { return m_compositingProperties.compositingReasons; }
 
+    friend class CompositingReasonFinder;

[ojan, 2014/03/21 17:12:06]

Instead of adding to the friend madness in RenderLayer, could we just make the
right things off CompositingReasonFinder public?

[abarth-chromium, 2014/03/21 17:16:13]

Sure.  Will do.

     friend class CompositedLayerMapping;
     friend class RenderLayerCompositor;
     friend class RenderLayerModelObject;
 
 private:
     LayerType m_layerType;
 
     // Self-painting layer is an optimization where we avoid the heavy RenderLayer painting
     // machinery for a RenderLayer allocated only to handle the overflow clip case.
     // FIXME(crbug.com/332791): Self-painting layer should be merged into the overflow-only concept.
@@ skipping 128 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