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

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

 /*
  * 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 215 matching lines @@
     void mediaPlayerPlayingRemotelyChanged(HTMLMediaElement mediaElement, boolean remote);
 
     void registerURLSchemeAsBypassingContentSecurityPolicy(DOMString scheme);
     void registerURLSchemeAsBypassingContentSecurityPolicy(DOMString scheme, sequence<DOMString> policyAreas);
     void removeURLSchemeRegisteredAsBypassingContentSecurityPolicy(DOMString scheme);
 
     TypeConversions typeConversions();
 
     sequence<DOMString> getReferencedFilePaths();
 
+    [RaisesException] void startStoringCompositedLayerDebugInfo(Document document);
+    [RaisesException] void stopStoringCompositedLayerDebugInfo(Document document);
+
     // These functions both reset the tracked repaint rects. They are intended to be used in the following order:
     //  startTrackingRepaints(), repaintRectsAsText(), stopTrackingRepaints().
     [RaisesException] void startTrackingRepaints(Document document);
     [RaisesException] void stopTrackingRepaints(Document document);
 
     // |node| should be Document, HTMLIFrameElement, or unspecified.
     // If |node| is an HTMLIFrameElement, it assumes node.contentDocument is
     // specified without security checks. Unspecified means this document.
     [RaisesException] void updateLayoutIgnorePendingStylesheetsAndRunPostLayoutTasks(optional Node? node = null);
 
@@ skipping 104 matching lines @@
     DOMString getProgrammaticScrollAnimationState(Node node);
 
     ClientRect visualRect(Node node);
 
     OriginTrialsTest originTrialsTest();
 
     void crash();
 
     void setIsLowEndDevice(boolean isLowEndDevice);
 };