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 4270ab576d2e43084f28ac99258d89c433f6be9a..9ff6a6785b41d99bf6a97f928de2e15452eca1e1 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, 
+                    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].