dart2js: Use an abstract Name class for names in the generated JavaScript ast.

sdk/lib/_internal/compiler/js_lib/js_helper.dart

 // Copyright (c) 2013, 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 _js_helper;
 
 import 'dart:_async_await_error_codes' as async_error_codes;
 
 import 'dart:_js_embedded_names' show
     DEFERRED_LIBRARY_URIS,
@@ skipping 129 matching lines @@
 bool builtinIsSubtype(type, String other) {
   return JS_BUILTIN('returns:bool;effects:none;depends:none',
                     JsBuiltin.isSubtype, other, type);
 }
 
 /// Returns true if the given [type] is _the_ `Function` type.
 // TODO(floitsch): move this to foreign_helper.dart or similar.
 @ForceInline()
 bool isDartFunctionTypeRti(Object type) {
   return JS_BUILTIN('returns:bool;effects:none;depends:none',
-                    JsBuiltin.isFunctionTypeRti, type);
+                    JsBuiltin.isGivenTypeRti, 

[floitsch, 2015/06/23 14:59:33]

Actually you might as well use rawRtiToJsConstructorName from above and write ==
yourself. Removes one builtin.

(Please add the necessary "effects:none;depends:none" in the rawRtiTo...
function)

+                    type,
+                    JS_GET_NAME(JsGetName.FUNCTION_CLASS_TYPE_NAME));
 }
 
 /// Returns whether the given type is _the_ Dart Object type.
 // TODO(floitsch): move this to foreign_helper.dart or similar.
 @ForceInline()
 bool isDartObjectTypeRti(type) {
   return JS_BUILTIN('returns:bool;effects:none;depends:none',
-                    JsBuiltin.isDartObjectTypeRti, type);
+                    JsBuiltin.isGivenTypeRti, 
+                    type,
+                    JS_GET_NAME(JsGetName.OBJECT_CLASS_TYPE_NAME));
 }
 
 /// Returns whether the given type is _the_ null type.
 // TODO(floitsch): move this to foreign_helper.dart or similar.
 @ForceInline()
 bool isNullTypeRti(type) {
   return JS_BUILTIN('returns:bool;effects:none;depends:none',
-                    JsBuiltin.isNullTypeRti, type);
+                    JsBuiltin.isGivenTypeRti, 
+                    type,
+                    JS_GET_NAME(JsGetName.NULL_CLASS_TYPE_NAME));
 }
 
 /// Returns the metadata of the given [index].
 // TODO(floitsch): move this to foreign_helper.dart or similar.
 @ForceInline()
 getMetadata(int index) {
   return JS_BUILTIN('returns:var;effects:none;depends:none',
                     JsBuiltin.getMetadata, index);
 }
 
@@ skipping 3952 matching lines @@
   // This is a function that will return a helper function that does the
   // iteration of the sync*.
   //
   // Each invocation should give a body with fresh state.
   final dynamic /* js function */ _outerHelper;
 
   SyncStarIterable(this._outerHelper);
 
   Iterator get iterator => new SyncStarIterator(JS('', '#()', _outerHelper));
 }