VM: Fix bug in CHA for signature classes.

runtime/vm/cha_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/assert.h"
 #include "vm/cha.h"
 #include "vm/class_finalizer.h"
 #include "vm/globals.h"
 #include "vm/symbols.h"
 #include "vm/unit_test.h"
@@ skipping 106 matching lines @@
 
   EXPECT(CHA::HasSubclasses(kInstanceCid));
   EXPECT(!CHA::HasSubclasses(kSmiCid));
   EXPECT(!CHA::HasSubclasses(kNullCid));
   EXPECT(!CHA::HasSubclasses(kDynamicCid));
   EXPECT(!CHA::HasSubclasses(kVoidCid));
   EXPECT(CHA::HasSubclasses(class_a_id));
   EXPECT(CHA::HasSubclasses(class_b_id));
   EXPECT(!CHA::HasSubclasses(class_c_id));
   EXPECT(!CHA::HasSubclasses(class_d_id));
+
+  class Class& function_impl_class =
+      Class::Handle(Type::Handle(Isolate::Current()->object_store()->
+          function_impl_type()).type_class());
+  EXPECT(CHA::HasSubclasses(function_impl_class.id()));
 }
 
 }  // namespace dart