dart2js cps: Generate fast checks for 'is String' and 'is bool'.

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 '../../common/registry.dart' show
     Registry;
 import '../../compiler.dart' show
@@ skipping 234 matching lines @@
   bool operatorEqHandlesNullArgument(FunctionElement element) {
     return _backend.operatorEqHandlesNullArgument(element);
   }
 
   bool hasStrictSubtype(ClassElement element) {
     return _compiler.world.hasAnyStrictSubtype(element);
   }
 
   ClassElement get jsExtendableArrayClass => _backend.jsExtendableArrayClass;
   ClassElement get jsMutableArrayClass => _backend.jsMutableArrayClass;
+
+  bool isStringClass(ClassElement classElement) =>
+      classElement == _backend.jsStringClass ||
+      classElement == _compiler.stringClass;
+
+  bool isBoolClass(ClassElement classElement) =>
+      classElement == _backend.jsBoolClass ||
+      classElement == _compiler.boolClass;
 }