String+ does not exist anymore. Fix issue #3857.

tests/compiler/dart2js_extra/this_phi_elimination_test.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.
 
 class A {
   foo(a) {
     while (false) {
-      // This call will make the builder want to put this as a phi.
+      // This call will make the builder want to put [this] as a phi.
       foo(0);
     }
     // This computation makes sure there will be a bailout version.
     return a + 42;
   }
 }
 
 main() {
   Expect.equals(42, new A().foo(0));
-  Expect.equals("42", new A().foo(""));
+  bool caughtException = false;

[kasperl, 2012/08/17 11:30:53]

Use Expect.throws(() => new A().foo(""), (e) => e is NoSuchMethodException)?

[ngeoffray, 2012/08/17 11:48:04]

Good point. Done.

+  try {
+    Expect.equals("42", new A().foo(""));
+  } catch (NoSuchMethodException ex) {
+    caughtException = true;
+  }
+  Expect.isTrue(caughtException);
 }