Improve hashCode for closures

runtime/vm/bootstrap.cc

Index: runtime/vm/bootstrap.cc
diff --git a/runtime/vm/bootstrap.cc b/runtime/vm/bootstrap.cc
index 8aa507588ef391e294a31422004c79d288d3e23f..2d015f84d842da0f52c90bd90a30af993749d399 100644
--- a/runtime/vm/bootstrap.cc
+++ b/runtime/vm/bootstrap.cc
@@ -232,7 +232,7 @@ static void Finish(Thread* thread, bool from_kernel) {
 #if defined(DEBUG)
   // Verify that closure field offsets are identical in Dart and C++.
   const Array& fields = Array::Handle(zone, cls.fields());
-  ASSERT(fields.Length() == 4);
+  ASSERT(fields.Length() == 5);
   Field& field = Field::Handle(zone);
   field ^= fields.At(0);
   ASSERT(field.Offset() == Closure::instantiator_type_arguments_offset());
@@ -242,6 +242,8 @@ static void Finish(Thread* thread, bool from_kernel) {
   ASSERT(field.Offset() == Closure::function_offset());
   field ^= fields.At(3);
   ASSERT(field.Offset() == Closure::context_offset());
+  field ^= fields.At(4);
+  ASSERT(field.Offset() == Closure::cached_hash_code_offset());
 #endif  // defined(DEBUG)
 
   // Eagerly compile Bool class, bool constants are used from within compiler.