VM: Fix CHA for Object.

runtime/vm/cha.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 "vm/cha.h"
 #include "vm/class_table.h"
 #include "vm/flags.h"
 #include "vm/freelist.h"
 #include "vm/object.h"
 #include "vm/raw_object.h"
@@ skipping 55 matching lines @@
   ASSERT(!cls.IsNull());
   ZoneGrowableArray<intptr_t>* ids = new ZoneGrowableArray<intptr_t>();
   CollectSubclassIds(ids, cls);
   return ids;
 }
 
 
 bool CHA::HasOverride(const Class& cls, const String& function_name) {
   const GrowableObjectArray& cls_direct_subclasses =
       GrowableObjectArray::Handle(cls.direct_subclasses());
+  // Subclasses of Object are not tracked by CHA. Safely assume that overrides
+  // exist.
+  if (cls.IsObjectClass()) return true;
+
   if (cls_direct_subclasses.IsNull()) {
     return false;
   }
   Class& direct_subclass = Class::Handle();
   for (intptr_t i = 0; i < cls_direct_subclasses.Length(); i++) {
     direct_subclass ^= cls_direct_subclasses.At(i);
     if (direct_subclass.LookupDynamicFunction(function_name) !=
         Function::null()) {
       return true;
     }
@@ skipping 30 matching lines @@
   ASSERT(!function.IsNull());
   ASSERT(function.IsDynamicFunction());
   const Class& function_owner = Class::Handle(function.Owner());
   const String& function_name = String::Handle(function.name());
   ZoneGrowableArray<intptr_t>* cids = new ZoneGrowableArray<intptr_t>();
   CollectSubclassIds(cids, function_owner);
   return GetNamedInstanceFunctionsOf(*cids, function_name);
 }
 
 }  // namespace dart