[SPv2] Introduce an option to output the GraphicsLayer tree as a flat layer list.

third_party/WebKit/Source/platform/graphics/GraphicsLayerClient.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 37 matching lines @@
 typedef unsigned GraphicsLayerPaintingPhase;
 
 enum {
     LayerTreeNormal = 0,
     LayerTreeIncludesDebugInfo = 1 << 0, // Dump extra debugging info like layer addresses.
     LayerTreeIncludesPaintInvalidations = 1 << 1,
     LayerTreeIncludesPaintingPhases = 1 << 2,
     LayerTreeIncludesRootLayer = 1 << 3,
     LayerTreeIncludesClipAndScrollParents = 1 << 4,
     LayerTreeIncludesCompositingReasons = 1 << 5,
+    OutputChildrenAsLayerList = 1 << 6, // Outputs all children of the given layer as a layer list, in paint order.
 };
 typedef unsigned LayerTreeFlags;
 
 class PLATFORM_EXPORT GraphicsLayerClient {
 public:
     virtual ~GraphicsLayerClient() {}
 
     virtual void notifyPaint(bool isFirstPaint, bool textPainted, bool imagePainted) { }
 
     virtual IntRect computeInterestRect(const GraphicsLayer*, const IntRect& previousInterestRect) const = 0;
@@ skipping 12 matching lines @@
     // This is executed in GraphicsLayer construction and destruction
     // to verify that we don't create or destroy GraphicsLayers
     // while painting.
     virtual void verifyNotPainting() { }
 #endif
 };
 
 } // namespace blink
 
 #endif // GraphicsLayerClient_h