Add support for abortion in v8::OutputStream.

src/profile-generator.h

Index: src/profile-generator.h
diff --git a/src/profile-generator.h b/src/profile-generator.h
index e5d7f2d622424146beeb1a86f40d009d2df8f4c9..c2bc4ce2835d1ecb99928c26141fd8cdc4d10e46 100644
--- a/src/profile-generator.h
+++ b/src/profile-generator.h
@@ -1003,6 +1003,7 @@ class HeapSnapshotJSONSerializer {
   int GetNodeId(HeapEntry* entry);
   int GetStringId(const char* s);
   void SerializeEdge(HeapGraphEdge* edge);
+  void SerializeImpl();
   void SerializeNode(HeapEntry* entry);
   void SerializeNodes();
   void SerializeSnapshot();