Add string.trimLeft/trimRight.

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 272 matching lines @@
    * Returns the substring of this string that extends from [startIndex],
    * inclusive, to [endIndex], exclusive.
    *
    *     var string = 'dartlang';
    *     string.substring(1);    // 'artlang'
    *     string.substring(1, 4); // 'art'
    */
   String substring(int startIndex, [int endIndex]);
 
   /**
-   * Removes leading and trailing whitespace from a string.
+   * Returns the string without any leading and trailing whitespace.
    *
    * If the string contains leading or trailing whitespace, a new string with no
    * leading and no trailing whitespace is returned:
    *
    *     '\tDart is fun\n'.trim(); // 'Dart is fun'
    *
    * Otherwise, the original string itself is returned:
    *
    *     var str1 = 'Dart';
    *     var str2 = str1.trim();
@@ skipping 15 matching lines @@
    *     2029          ; White_Space # Zp   PARAGRAPH SEPARATOR
    *     202F          ; White_Space # Zs   NARROW NO-BREAK SPACE
    *     205F          ; White_Space # Zs   MEDIUM MATHEMATICAL SPACE
    *     3000          ; White_Space # Zs   IDEOGRAPHIC SPACE
    *
    *     FEFF          ; BOM                ZERO WIDTH NO_BREAK SPACE
    */
   String trim();
 
   /**
+   * Returns the string without any leading whitespace.
+   *
+   * As [trim], but only removes leading whitespace.
+   */
+  String trimLeft();
+
+  /**
+   * Returns the string without any trailing whitespace.
+   *
+   * As [trim], but only removes trailing whitespace.
+   */
+  String trimRight();
+
+  /**
    * Creates a new string by concatenating this string with itself a number
    * 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);
 
@@ skipping 378 matching lines @@
         _position = position - 1;
         _currentCodePoint = _combineSurrogatePair(prevCodeUnit, codeUnit);
         return true;
       }
     }
     _position = position;
     _currentCodePoint = codeUnit;
     return true;
   }
 }