Change how runtime type information is being set in the backend.

lib/compiler/implementation/ssa/nodes.dart

 // 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.
 
 interface HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 2398 matching lines @@
                        HInstruction typeInfo, [this.nullOk = false])
     : super(<HInstruction>[expression, typeInfo]);
 
   HIs(this.typeExpression, HInstruction expression, [this.nullOk = false])
      : super(<HInstruction>[expression]);
 
   HInstruction get expression => inputs[0];
 
   HInstruction get typeInfoCall => inputs[1];
 
+  bool hasTypeInfo() => inputs.length == 2;
+
   HType get guaranteedType => HType.BOOLEAN;
 
   accept(HVisitor visitor) => visitor.visitIs(this);
 
   toString() => "$expression is $typeExpression";
 }
 
 class HTypeConversion extends HCheck {
   HType type;
   final int kind;
@@ skipping 370 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }