Expose last seen heap object id via v8 public api.

src/heap-profiler.h

 // Copyright 2009-2010 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 40 matching lines @@
 
   static HeapSnapshot* TakeSnapshot(const char* name,
                                     int type,
                                     v8::ActivityControl* control);
   static HeapSnapshot* TakeSnapshot(String* name,
                                     int type,
                                     v8::ActivityControl* control);
 
   static void StartHeapObjectsTracking();
   static void StopHeapObjectsTracking();
-  static void PushHeapObjectsStats(OutputStream* stream);
+  static SnapshotObjectId PushHeapObjectsStats(OutputStream* stream);
   static int GetSnapshotsCount();
   static HeapSnapshot* GetSnapshot(int index);
   static HeapSnapshot* FindSnapshot(unsigned uid);
   static SnapshotObjectId GetSnapshotObjectId(Handle<Object> obj);
   static void DeleteAllSnapshots();
 
   void ObjectMoveEvent(Address from, Address to);
 
   void DefineWrapperClass(
       uint16_t class_id, v8::HeapProfiler::WrapperInfoCallback callback);
@@ skipping 10 matching lines @@
   HeapSnapshot* TakeSnapshotImpl(const char* name,
                                  int type,
                                  v8::ActivityControl* control);
   HeapSnapshot* TakeSnapshotImpl(String* name,
                                  int type,
                                  v8::ActivityControl* control);
   void ResetSnapshots();
 
   void StartHeapObjectsTrackingImpl();
   void StopHeapObjectsTrackingImpl();
-  void PushHeapObjectsStatsImpl(OutputStream* stream);
+  SnapshotObjectId PushHeapObjectsStatsImpl(OutputStream* stream);
 
   HeapSnapshotsCollection* snapshots_;
   unsigned next_snapshot_uid_;
   List<v8::HeapProfiler::WrapperInfoCallback> wrapper_callbacks_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_PROFILER_H_