Bug cleanup: change String.trim comment to be less ambiguous.

lib/core/string.dart

Index: lib/core/string.dart
diff --git a/lib/core/string.dart b/lib/core/string.dart
index 4b852131de063d03c68682ecd9a773fbc47894bb..0d733efe3d8ade0aeb547921b89ad1419d288064 100644
--- a/lib/core/string.dart
+++ b/lib/core/string.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -78,9 +78,10 @@ interface String
   String substring(int startIndex, [int endIndex]);
 
   /**
-   * Returns a new string where leading and trailing whitespaces of
-   * this string have been removed, or returns this string if it does
-   * not have leading and trailing whitespaces.
+   * Removes leading and trailing whitespace from a string. If the
+   * string contains leading or trailing whitespace a new string with
+   * no leading and no trailing whitespace is returned. Otherwise, the
+   * string itself is returned.
    */
   String trim();