Generate all runtime files from dart.

tool/input_sdk/private/foreign_helper.dart

 // Copyright (c) 2012, 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 dart._foreign_helper;
 
 /**
  * Emits a JavaScript code fragment parameterized by arguments.
  *
  * Hash characters `#` in the [codeTemplate] are replaced in left-to-right order
@@ skipping 263 matching lines @@
 }
 
 /**
  * JavaScript string concatenation. Inputs must be Strings.  Corresponds to the
  * HStringConcat SSA instruction and may be constant-folded.
  */
 String JS_STRING_CONCAT(String a, String b) {
   // This body is unused, only here for type analysis.
   return JS('String', '# + #', a, b);
 }
+
+/// Same `@rest` annotation and `spread` function as in
+/// `package:js/src/varargs.dart`.
+///
+/// Runtime files cannot import packages, which is why we have an ad-hoc copy.
+
+class _Rest {
+  const _Rest();
+}
+
+const _Rest rest = const _Rest();
+
+dynamic spread(args) {
+  throw new StateError(
+      'The spread function cannot be called, '
+      'it should be compiled away.');
+}