Fix Unicode issues in dart2js and dart2dart.

sdk/lib/core/string.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.
 
 /**
  * The String class represents character strings. Strings are
  * immutable. A string is represented by a list of 32-bit Unicode
  * scalar character codes accessible through the [charCodeAt] or the
  * [charCodes] method.
  */
@@ skipping 58 matching lines @@
    */
   String concat(String other);
 
   /**
    * Returns a substring of this string in the given range.
    * [startIndex] is inclusive and [endIndex] is exclusive.
    */
   String substring(int startIndex, [int endIndex]);
 
   /**
-   * 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.
+   * 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.  Whitespace is defined as every Unicode character in the Zs, Zl
+   * and Zp categories (this includes no-break space), the spacing control
+   * characters from 9 to 13 (tab, lf, vtab, ff and cr), and 0xfeff the BOM
+   * character.
    */
   String trim();
 
   /**
    * Returns whether this string contains [other] starting
    * at [startIndex] (inclusive).
    */
   bool contains(Pattern other, [int startIndex]);
 
   /**
@@ skipping 29 matching lines @@
    * where all characters  are made lower case. Returns [:this:] otherwise.
    */
   String toLowerCase();
 
   /**
    * If this string is not already all uper case, returns a new string
    * where all characters are made upper case. Returns [:this:] otherwise.
    */
   String toUpperCase();
 }