Cache hash code for closures.

runtime/vm/raw_object_snapshot.cc

Index: runtime/vm/raw_object_snapshot.cc
diff --git a/runtime/vm/raw_object_snapshot.cc b/runtime/vm/raw_object_snapshot.cc
index 7827445ebd9b9c3402bc7933afcd641c9feed0a9..77f057609b6ca60c31d4df18801ede1f57a33e4b 100644
--- a/runtime/vm/raw_object_snapshot.cc
+++ b/runtime/vm/raw_object_snapshot.cc
@@ -590,7 +590,8 @@ RawClosureData* ClosureData::ReadFrom(SnapshotReader* reader,
   reader->AddBackRef(object_id, &data, kIsDeserialized);
 
   // Set all the object fields.
-  READ_OBJECT_FIELDS(data, data.raw()->from(), data.raw()->to(),
+  // Cached hash is null-initialized by ClosureData::New()
+  READ_OBJECT_FIELDS(data, data.raw()->from(), data.raw()->to_snapshot(),
                      kAsInlinedObject);
 
   return data.raw();