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

sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart

Index: sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart b/sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart
index 734ddb95db7808e5f54e4ca175de557ede530502..8e11da34fd44553388c53d9d5a48c826fa819a79 100644
--- a/sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart
+++ b/sdk/lib/_internal/compiler/js_lib/shared/embedded_names.dart
@@ -117,6 +117,12 @@ enum JsGetName {
   /// Field name used for determining if an object or its interceptor has
   /// JavaScript indexing behavior.
   IS_INDEXABLE_FIELD_NAME,
+  /// String representation of the type of the null class.
+  NULL_CLASS_TYPE_NAME,
+  /// String representation of the type of the object class.
+  OBJECT_CLASS_TYPE_NAME,
+  /// String representation of the type of the function class.
+  FUNCTION_CLASS_TYPE_NAME,
 }
 
 enum JsBuiltin {
@@ -172,25 +178,13 @@ enum JsBuiltin {
   ///                JsBuiltin.isSubtype, other, type);
   isSubtype,
 
-  /// Returns true if the given type is _the_ `Function` type.
-  /// That is, it returns true if the given [type] is exactly the `Function`
-  /// type rti-encoding.
+  /// Returns true if the given type equals the type given as second
+  /// argument. Use the JS_GET_NAME helpers to get the type representation
+  /// for various Dart classes.
   ///
   ///     JS_BUILTIN('returns:bool;effects:none;depends:none',
-  ///                JsBuiltin.isFunctionTypeLiteral, type);
-  isFunctionTypeRti,
-
-  /// Returns whether the given type is _the_ null-type..
-  ///
-  ///     JS_BUILTIN('returns:bool;effects:none;depends:none',
-  ///                JsBuiltin.isNullType, type);
-  isNullTypeRti,
-
-  /// Returns whether the given type is _the_ Dart Object type.
-  ///
-  ///     JS_BUILTIN('returns:bool;effects:none;depends:none',
-  ///                JsBuiltin.isDartObjectType, type);
-  isDartObjectTypeRti,
+  ///                JsBuiltin.isFunctionTypeLiteral, type, name);
+  isGivenTypeRti,
 
   /// Returns the metadata of the given [index].
   ///