Split nodes and edges into separate arrays in heap snapshot serialization.

src/profile-generator.h

Index: src/profile-generator.h
diff --git a/src/profile-generator.h b/src/profile-generator.h
index 1fa647eef1df03e3e6d1ba819cfb32e51d09efb5..0d5474d418062a1603f1a94bbebb6383db1ac75c 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -1145,10 +1145,11 @@ class HeapSnapshotJSONSerializer {
 
   HeapSnapshot* CreateFakeSnapshot();
   int GetStringId(const char* s);
-  void SerializeEdge(HeapGraphEdge* edge);
+  void SerializeEdge(HeapGraphEdge* edge, bool first_edge);
+  void SerializeEdges(const List<HeapEntry*>& nodes);
   void SerializeImpl();
-  void SerializeNode(HeapEntry* entry);
-  void SerializeNodes();
+  void SerializeNode(HeapEntry* entry, int edges_index);
+  void SerializeNodes(const List<HeapEntry*>& nodes);
   void SerializeSnapshot();
   void SerializeString(const unsigned char* s);
   void SerializeStrings();