Add optional debugging output of what paint chunks go into what layers.

third_party/WebKit/Source/core/testing/Internals.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 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.
@@ skipping 369 matching lines @@
 
   TypeConversions* typeConversions() const;
   PrivateScriptTest* privateScriptTest() const;
   DictionaryTest* dictionaryTest() const;
   UnionTypesTest* unionTypesTest() const;
   OriginTrialsTest* originTrialsTest() const;
   CallbackFunctionTest* callbackFunctionTest() const;
 
   Vector<String> getReferencedFilePaths() const;
 
+  void startStoringCompositedLayerDebugInfo(Document*, ExceptionState&);
+  void stopStoringCompositedLayerDebugInfo(Document*, ExceptionState&);
+
   void startTrackingRepaints(Document*, ExceptionState&);
   void stopTrackingRepaints(Document*, ExceptionState&);
   void updateLayoutIgnorePendingStylesheetsAndRunPostLayoutTasks(
       Node*,
       ExceptionState&);
   void forceFullRepaint(Document*, ExceptionState&);
 
   ClientRectList* draggableRegions(Document*, ExceptionState&);
   ClientRectList* nonDraggableRegions(Document*, ExceptionState&);
 
@@ skipping 140 matching lines @@
                            ExceptionState&);
   Member<InternalRuntimeFlags> m_runtimeFlags;
   Member<Document> m_document;
 
   IterationSource* startIteration(ScriptState*, ExceptionState&) override;
 };
 
 }  // namespace blink
 
 #endif  // Internals_h