[Invalidation tracking] Add trace events for layout invalidations

Source/core/inspector/InspectorTraceEvents.h

Index: Source/core/inspector/InspectorTraceEvents.h
diff --git a/Source/core/inspector/InspectorTraceEvents.h b/Source/core/inspector/InspectorTraceEvents.h
index 7f088b6fbc3e2388d55296fb43d7cc0ae18c7a3c..de017cc8891fbfc39fa0ef513e318664d2b40213 100644
--- a/Source/core/inspector/InspectorTraceEvents.h
+++ b/Source/core/inspector/InspectorTraceEvents.h
@@ -35,6 +35,11 @@ public:
     static PassRefPtr<TraceEvent::ConvertableToTraceFormat> endData(RenderObject* rootForThisLayout);
 };
 
+class InspectorLayoutInvalidationTrackingEvent {
+public:
+    static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(const RenderObject*);
+};
+
 class InspectorSendRequestEvent {
 public:
     static PassRefPtr<TraceEvent::ConvertableToTraceFormat> data(unsigned long identifier, LocalFrame*, const ResourceRequest&);