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

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

Index: sdk/lib/_internal/compiler/js_lib/js_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/js_helper.dart b/sdk/lib/_internal/compiler/js_lib/js_helper.dart
index 15f22c82bf0ccdd506be8901a516d9644ff7a4b9..6bf3e9c01b257ca3c4ad5e2f10d1e8d1700ad4ac 100644
--- a/sdk/lib/_internal/compiler/js_lib/js_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/js_helper.dart
@@ -147,7 +147,9 @@ bool builtinIsSubtype(type, String other) {
 @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.
@@ -155,7 +157,9 @@ bool isDartFunctionTypeRti(Object type) {
 @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.
@@ -163,7 +167,9 @@ bool isDartObjectTypeRti(type) {
 @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].