Issue trace events to gather repaint information.

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index a4d483d79055044d9442017b0163d0681bb7a0f1..e17253b3044d0ee16ada04ddc698262f7c213eaa 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -117,6 +117,20 @@ enum MapCoordinatesMode {
 };
 typedef unsigned MapCoordinatesFlags;
 
+enum InvalidationReason {
+    InvalidationIncremental,
+    InvalidationSelfLayout,
+    InvalidationBorderFitLines,
+    InvalidationBorderRadius,
+    InvalidationBoundsChangeWithBackground,
+    InvalidationBoundsChange,
+    InvalidationScroll,
+    InvalidationSelection,
+    InvalidationLayer,
+    InvalidationRepaint,
+    InvalidationRepaintRectangle
+};
+
 const int caretWidth = 1;
 
 struct AnnotatedRegionValue {
@@ -801,9 +815,10 @@ public:
     // if painting is root-relative. This is the container that should be passed to the 'forRepaint'
     // methods.
     RenderLayerModelObject* containerForRepaint() const;
+
     // Actually do the repaint of rect r for this object which has been computed in the coordinate space
     // of repaintContainer. If repaintContainer is 0, repaint via the view.
-    void repaintUsingContainer(const RenderLayerModelObject* repaintContainer, const IntRect&) const;
+    void repaintUsingContainer(const RenderLayerModelObject* repaintContainer, const IntRect&, InvalidationReason) const;
 
     // Repaint the entire object.  Called when, e.g., the color of a border changes, or when a border
     // style changes.
@@ -1068,6 +1083,7 @@ private:
 #ifndef NDEBUG
     void checkBlockPositionedObjectsNeedLayout();
 #endif
+    const char* invalidationReasonToString(InvalidationReason) const;
 
     RefPtr<RenderStyle> m_style;