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

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

Index: third_party/WebKit/Source/core/testing/Internals.idl
diff --git a/third_party/WebKit/Source/core/testing/Internals.idl b/third_party/WebKit/Source/core/testing/Internals.idl
index e42677a9c8e4547481b468eef9aa0026e6489ccf..0b863b798e052f1097ad89ec44b56cd43c3fdd79 100644
--- a/third_party/WebKit/Source/core/testing/Internals.idl
+++ b/third_party/WebKit/Source/core/testing/Internals.idl
@@ -233,6 +233,9 @@
 
     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);