[Invalidation Tracking] Include DescendantInvalidationSet id in trace events

Source/core/css/invalidation/DescendantInvalidationSet.cpp

 /*
  * Copyright (C) 2014 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 203 matching lines @@
     visitor->trace(m_ids);
     visitor->trace(m_tagNames);
     visitor->trace(m_attributes);
 #endif
 }
 
 void DescendantInvalidationSet::toTracedValue(TracedValue* value) const
 {
     value->beginDictionary();
 
+    value->setString("id", descendantInvalidationSetToIdString(*this));
+
     if (m_allDescendantsMightBeInvalid)
         value->setBoolean("allDescendantsMightBeInvalid", true);
     if (m_customPseudoInvalid)
         value->setBoolean("customPseudoInvalid", true);
     if (m_treeBoundaryCrossing)
         value->setBoolean("treeBoundaryCrossing", true);
     if (m_insertionPointCrossing)
         value->setBoolean("insertionPointCrossing", true);
 
     if (m_ids) {
@@ skipping 32 matching lines @@
 {
     RefPtr<TracedValue> value = TracedValue::create();
     value->beginArray("DescendantInvalidationSet");
     toTracedValue(value.get());
     value->endArray();
     fprintf(stderr, "%s\n", value->asTraceFormat().ascii().data());
 }
 #endif // NDEBUG
 
 } // namespace blink