Fix typo in padLeft/padRight documentation.

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.
 
 part of dart.core;
 
 /**
  * A sequence of characters.
  *
  * A string can be either single or multiline. Single line strings are
@@ skipping 342 matching lines @@
    * of times.
    *
    * The result of `str * n` is equivalent to
    * `str + str + ...`(n times)`... + str`.
    *
    * Returns an empty string if [times] is zero or negative.
    */
   String operator *(int times);
 
   /**
-   * Pads this string on the left if it is shorther than [width].
+   * Pads this string on the left if it is shorter than [width].
    *
    * Return a new string that prepends [padding] onto this string
    * one time for each position the length is less than [width].
    *
    * If [width] is already smaller than or equal to `this.length`,
    * no padding is added. A negative `width` is treated as zero.
    *
    * If [padding] has length different from 1, the result will not
    * have length `width`. This may be useful for cases where the
    * padding is a longer string representing a single character, like
    * `" "` or `"\u{10002}`".
    * In that case, the user should make sure that `this.length` is
    * the correct measure of the strings length.
    */
   String padLeft(int width, [String padding = ' ']);
 
   /**
-   * Pads this string on the right if it is shorther than [width].
+   * Pads this string on the right if it is shorter than [width].
    *
    * Return a new string that appends [padding] after this string
    * one time for each position the length is less than [width].
    *
    * If [width] is already smaller than or equal to `this.length`,
    * no padding is added. A negative `width` is treated as zero.
    *
    * If [padding] has length different from 1, the result will not
    * have length `width`. This may be useful for cases where the
    * padding is a longer string representing a single character, like
@@ skipping 391 matching lines @@
         _position = position - 1;
         _currentCodePoint = _combineSurrogatePair(prevCodeUnit, codeUnit);
         return true;
       }
     }
     _position = position;
     _currentCodePoint = codeUnit;
     return true;
   }
 }