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

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index f3496595a49b91242f2929265d357eb26dab8317..749f2d99b9a53621278905758c8d64c43fd1c886 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -358,6 +358,10 @@ class CORE_EXPORT FrameView final
 
   static void setInitialTracksPaintInvalidationsForTesting(bool);
 
+  void setIsStoringCompositedLayerDebugInfo(bool val) {
+    m_isStoringCompositedLayerDebugInfo = val;
+  }
+
   // These methods are for testing.
   void setTracksPaintInvalidations(bool);
   bool isTrackingPaintInvalidations() const {
@@ -1132,6 +1136,7 @@ class CORE_EXPORT FrameView final
   // For Slimming Paint v2 only.
   std::unique_ptr<PaintController> m_paintController;
   std::unique_ptr<PaintArtifactCompositor> m_paintArtifactCompositor;
+  bool m_isStoringCompositedLayerDebugInfo;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count) {