frog: better binding of methods.

tests/language/src/MethodBindingTest.dart

 // Copyright (c) 2011, 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.
 
 // Bind a method to a variable that can be invoked as a function
 
 class A {
   int a;
 
   static var func;
@@ skipping 106 matching lines @@
     Expect.equals(4, f13());
 
     var o14 = new D(14);
     Function f14 = o14.getSuper();
     Expect.equals(14, f14());
 
     // Assign static field to a function and invoke it.
     A.func = A.foo;
     Expect.equals(4, A.func());
 
+    // bind a function that is possibly native in Javascript.
+    String o15 = 'hithere';
+    var f15 = o15.substring;
+    Expect.equals('i', f15(1, 2));
+
+    var o16 = 'hithere';
+    var f16 = o16.substring;
+    Expect.equals('i', f16(1, 2));
+
+    var f17 = 'hithere'.substring;
+    Expect.equals('i', f17(1, 2));
   }
 
   static testMain() {
     test();
   }
 }
 
 main() {
   MethodBindingTest.testMain();
 }