Use Double::NewCanonical instead of creating a double object and then canonicalizing it.

vm/ast.cc

 // Copyright (c) 2011, 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/ast.h"
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/isolate.h"
 #include "vm/object_store.h"
 #include "vm/resolver.h"
@@ skipping 75 matching lines @@
     if (literal().IsSmi()) {
       const Smi& smi = Smi::Cast(literal());
       const Instance& literal =
           Instance::ZoneHandle(Integer::New(-smi.Value()));
       return new LiteralNode(this->token_pos(), literal);
     }
     if (literal().IsDouble()) {
       const Double& dbl = Double::Cast(literal());
       // Preserve negative zero.
       double new_value = (dbl.value() == 0.0) ? -0.0 : (0.0 - dbl.value());
-      Double& double_instance =
-          Double::ZoneHandle(Double::New(new_value, Heap::kOld));
-      double_instance ^= double_instance.Canonicalize();
+      const Double& double_instance =
+          Double::ZoneHandle(Double::NewCanonical(new_value));
       return new LiteralNode(this->token_pos(), double_instance);
     }
   }
   return NULL;
 }
 
 
 bool ComparisonNode::IsKindValid() const {
   return Token::IsRelationalOperator(kind_)
       || Token::IsEqualityOperator(kind_)
@@ skipping 325 matching lines @@
   if (result.IsError() || result.IsNull()) {
     // TODO(turnidge): We could get better error messages by returning
     // the Error object directly to the parser.  This will involve
     // replumbing all of the EvalConstExpr methods.
     return NULL;
   }
   return &Instance::ZoneHandle(Instance::Cast(result).raw());
 }
 
 }  // namespace dart