Add field names to Code, ConsString, and JSGlobalPropertyCell in heap snapshot.

src/profile-generator.h

Index: src/profile-generator.h
diff --git a/src/profile-generator.h b/src/profile-generator.h
index 1468777fc77d7684e1b0b4c4d65dbe898e53b980..0f8481f9946fa47f1f980c8b75c4936765104bd1 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -986,6 +986,8 @@ class V8HeapExplorer : public HeapEntriesAllocator {
   void ExtractScript(HeapEntry* entry, Script* script);
   void ExtractCodeCache(HeapEntry* entry, CodeCache* code_cache);
   void ExtractCode(HeapEntry* entry, Code* code);
+  void ExtractJSGlobalPropertyCell(HeapEntry* entry,
+                                   JSGlobalPropertyCell* cell);
   void ExtractClosureReferences(JSObject* js_obj, HeapEntry* entry);
   void ExtractPropertyReferences(JSObject* js_obj, HeapEntry* entry);
   void ExtractElementReferences(JSObject* js_obj, HeapEntry* entry);