dart2js cps_ir: Use interceptors for is-checks (version 2)

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

 // Copyright (c) 2014, 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 tree_ir_builder;
 
 import '../diagnostics/invariant.dart' show
     InternalErrorFunction;
 import '../diagnostics/spannable.dart' show
     CURRENT_ELEMENT_SPANNABLE;
@@ skipping 623 matching lines @@
         node.dartType,
         node.arguments.map(getVariableUse).toList());
   }
 
   Expression visitTypeTest(cps_ir.TypeTest node) {
     Expression value = getVariableUse(node.value);
     List<Expression> typeArgs = translateArguments(node.typeArguments);
     return new TypeOperator(value, node.dartType, typeArgs, isTypeTest: true);
   }
 
+  Expression visitTypeTestViaFlag(cps_ir.TypeTestViaFlag node) {
+    Expression value = getVariableUse(node.interceptor);
+    // TODO(sra): Move !! to cps_ir level.
+    return new Not(new Not(new GetTypeTestProperty(value, node.dartType)));
+  }
+
   Expression visitGetStatic(cps_ir.GetStatic node) {
     return new GetStatic(node.element, node.sourceInformation);
   }
 
   Expression visitSetStatic(cps_ir.SetStatic node) {
     return new SetStatic(
         node.element,
         getVariableUse(node.value),
         node.sourceInformation);
   }
@@ skipping 39 matching lines @@
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node');
   }
 
   visitFunctionDefinition(cps_ir.FunctionDefinition node) {
     unexpectedNode(node);
   }
   visitParameter(cps_ir.Parameter node) => unexpectedNode(node);
   visitContinuation(cps_ir.Continuation node) => unexpectedNode(node);
   visitMutableVariable(cps_ir.MutableVariable node) => unexpectedNode(node);
 }
-