Improve upper bound finalization in VM and fix #25122.

runtime/lib/mirrors.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 "lib/mirrors.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
@@ skipping 1188 matching lines @@
     }
   }
 
   return member_mirrors.raw();
 }
 
 
 DEFINE_NATIVE_ENTRY(ClassMirror_type_variables, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(MirrorReference, ref, arguments->NativeArgAt(0));
   const Class& klass = Class::Handle(ref.GetClassReferent());
+  const Error& error = Error::Handle(zone, klass.EnsureIsFinalized(thread));
+  if (!error.IsNull()) {
+    Exceptions::PropagateError(error);
+    UNREACHABLE();
+  }
   return CreateTypeVariableList(klass);
 }
 
 
 DEFINE_NATIVE_ENTRY(ClassMirror_type_arguments, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, type, arguments->NativeArgAt(0));
 
   const Class& cls = Class::Handle(type.type_class());
   const intptr_t num_params = cls.NumTypeParameters();
 
@@ skipping 887 matching lines @@
 }
 
 DEFINE_NATIVE_ENTRY(TypeMirror_subtypeTest, 2) {
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, a, arguments->NativeArgAt(0));
   GET_NON_NULL_NATIVE_ARGUMENT(AbstractType, b, arguments->NativeArgAt(1));
   return Bool::Get(a.IsSubtypeOf(b, NULL)).raw();
 }
 
 
 }  // namespace dart