dart2js cps_ir: Use interceptors for is-checks.

pkg/compiler/lib/src/cps_ir/insert_refinements.dart

 // Copyright (c) 2015, 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.
 
 library cps_ir.optimization.insert_refinements;
 
 import 'optimizers.dart' show Pass;
 import 'shrinking_reductions.dart' show ParentVisitor;
 import 'cps_ir_nodes.dart';
 import '../types/constants.dart';
@@ skipping 143 matching lines @@
 
     // If the condition is an 'is' check, promote the checked value.
     if (condition is TypeTest) {
       Primitive value = condition.value.definition;
       TypeMask type = types.subtypesOf(condition.dartType);
       Primitive refinedValue = new Refinement(value, type);
       pushRefinement(trueCont, refinedValue);
       push(falseCont);
       return;
     }
+    if (condition is TypeTestRaw) {
+      Primitive value = condition.value.definition;
+      TypeMask type = types.subtypesOf(condition.dartType);
+      Primitive refinedValue = new Refinement(value, type);
+      pushRefinement(trueCont, refinedValue);
+      push(falseCont);
+      return;
+    }
 
     // If the condition is comparison with a constant, promote the other value.
     // This can happen either for calls to `==` or `identical` calls, such
     // as the ones inserted by the unsugaring pass.
 
     void refineEquality(Primitive first,
                         Primitive second,
                         Continuation trueCont,
                         Continuation falseCont) {
       if (second is Constant && second.value.isNull) {
@@ skipping 41 matching lines @@
            cont.firstRef.parent is Branch)) {
         // Do not push the continuation here.
         // visitInvokeMethod and visitBranch will do that.
       } else {
         push(cont);
       }
     }
     return node.body;
   }
 }