dart2js cps: Always use interceptors and type tags for 'is' checks.

pkg/compiler/lib/src/js_backend/codegen/glue.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 code_generator_dependencies;
 
 import '../js_backend.dart';
 import '../../dart2jslib.dart';
 import '../../js_emitter/js_emitter.dart';
 import '../../js/js.dart' as js;
@@ skipping 181 matching lines @@
   js.Expression generateTypeRepresentation(DartType dartType,
                                            List<js.Expression> arguments) {
     int variableIndex = 0;
     js.Expression representation = _backend.rti.getTypeRepresentation(
         dartType,
         (_) => arguments[variableIndex++]);
     assert(variableIndex == arguments.length);
     return representation;
   }
 
-  bool isNativePrimitiveType(DartType type) {
-    if (type is! InterfaceType) return false;
-    return _backend.isNativePrimitiveType(type.element);
-  }
-
   void registerIsCheck(DartType type, Registry registry) {
     _enqueuer.registerIsCheck(type, registry);
     _backend.registerIsCheckForCodegen(type, _enqueuer, registry);
   }
 
-  bool isIntClass(ClassElement cls) => cls == _compiler.intClass;
-
-  bool isStringClass(ClassElement cls) => cls == _compiler.stringClass;
-
-  bool isBoolClass(ClassElement cls) => cls == _compiler.boolClass;
-
-  bool isNumClass(ClassElement cls) => cls == _compiler.numClass;
-
-  bool isDoubleClass(ClassElement cls) => cls == _compiler.doubleClass;
-
   String getTypeTestTag(DartType type) {
     return _backend.namer.operatorIsType(type);
   }
 
   bool operatorEqHandlesNullArgument(FunctionElement element) {
     return _backend.operatorEqHandlesNullArgument(element);
   }
-
-  bool isListClass(ClassElement cls) => cls == _compiler.listClass;
 }