Keep a trail while checking upper bounds in the VM in order to properly handle

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, 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 "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 3867 matching lines @@
   for (int i = 0; i < ic_data.NumberOfChecks(); i++) {
     cls = class_table.At(ic_data.GetReceiverClassIdAt(i));
     if (cls.NumTypeArguments() > 0) {
       return Bool::null();
     }
     const bool is_subtype = cls.IsSubtypeOf(
         TypeArguments::Handle(Z),
         type_class,
         TypeArguments::Handle(Z),
         NULL,
+        NULL,
         Heap::kOld);
     results->Add(cls.id());
     results->Add(is_subtype);
     if (prev.IsNull()) {
       prev = Bool::Get(is_subtype).raw();
     } else {
       if (is_subtype != prev.value()) {
         results_differ = true;
       }
     }
@@ skipping 74 matching lines @@
                                     const AbstractType& type) {
   ASSERT(results->length() >= 2);  // At least on eentry.
   const ClassTable& class_table = *Isolate::Current()->class_table();
   if ((*results)[0] != kSmiCid) {
     const Class& cls = Class::Handle(class_table.At(kSmiCid));
     const Class& type_class = Class::Handle(type.type_class());
     const bool smi_is_subtype = cls.IsSubtypeOf(TypeArguments::Handle(),
                                                 type_class,
                                                 TypeArguments::Handle(),
                                                 NULL,
+                                                NULL,
                                                 Heap::kOld);
     results->Add((*results)[results->length() - 2]);
     results->Add((*results)[results->length() - 2]);
     for (intptr_t i = results->length() - 3; i > 1; --i) {
       (*results)[i] = (*results)[i - 2];
     }
     (*results)[0] = kSmiCid;
     (*results)[1] = smi_is_subtype;
   }
 
@@ skipping 1053 matching lines @@
         // the code for this instruction, however, leaving the environment
         // changes code.
         current->RemoveEnvironment();
       }
     }
   }
 }
 
 
 }  // namespace dart