dart2js: Always generate functions for rti substitutions.

sdk/lib/_internal/compiler/js_lib/js_rti.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.
 
 /**
  * This part contains helpers for supporting runtime type information.
  *
  * The helper use a mixture of Dart and JavaScript objects. To indicate which is
  * used where we adopt the scheme of using explicit type annotation for Dart
  * objects and 'var' or omitted return type for JavaScript objects.
@@ skipping 214 matching lines @@
 }
 
 /**
  * Applies the [substitution] on the [arguments].
  *
  * See the comment in the beginning of this file for a description of the
  * possible values for [substitution].
  */
 substitute(var substitution, var arguments) {
   assert(isNull(substitution) ||
-         isJsArray(substitution) ||
          isJsFunction(substitution));
   assert(isNull(arguments) || isJsArray(arguments));
-  if (isJsArray(substitution)) {
-    arguments = substitution;
-  } else if (isJsFunction(substitution)) {
+  if (isJsFunction(substitution)) {
     substitution = invoke(substitution, arguments);
     if (isJsArray(substitution)) {
       arguments = substitution;
     } else if (isJsFunction(substitution)) {
       // TODO(johnniwinther): Check if this is still needed.
       arguments = invoke(substitution, arguments);
     }
   }
   return arguments;
 }
@@ skipping 446 matching lines @@
  * and [t] are Dart values.
  */
 bool isIdentical(var s, var t) => JS('bool', '# === #', s, t);
 
 /**
  * Returns [:true:] if the JavaScript values [s] and [t] are not identical. We
  * use this helper to avoid generating code under the invalid assumption that
  * [s] and [t] are Dart values.
  */
 bool isNotIdentical(var s, var t) => JS('bool', '# !== #', s, t);