Fix a typo in the documentation for HashMap.

sdk/lib/collection/hash_map.dart

 // Copyright (c) 2013, 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.collection;
 
 /** Default function for equality comparison in customized HashMaps */
 bool _defaultEquals(a, b) => a == b;
 /** Default function for hash-code computation in customized HashMaps */
 int _defaultHashCode(a) => a.hashCode;
 
 /** Type of custom equality function */
 typedef bool _Equality<K>(K a, K b);
 /** Type of custom hash code function. */
 typedef int _Hasher<K>(K object);
 
 /**
  * A hash-table based implementation of [Map].
  *
  * The keys of a `HashMap` must have consistent [Object.operator==]
  * and [Object.hashCode] implementations. This means that the `==` operator
  * must define a stable equivalence relation on the keys (reflexive,
  * symmetric, transitive, and consistent over time), and that `hashCode`
  * must be the same for objects that are considered equal by `==`.
  *
  * The map allows `null` as a key.
  *
  * Iterating the map's keys, values or entries (through [forEach])
  * may happen in any order.
- * The itearation order only changes when the map is modified.
+ * The iteration order only changes when the map is modified.
  * Values are iterated in the same order as their associated keys,
  * so iterating the [keys] and [values] in parallel
  * will give matching key and value pairs.
  */
 abstract class HashMap<K, V> implements Map<K, V> {
   /**
    * Creates an unordered hash-table based [Map].
    *
    * The created map is not ordered in any way. When iterating the keys or
    * values, the iteration order is unspecified except that it will stay the
@@ skipping 95 matching lines @@
    * overwrites the previous value.
    *
    * It is an error if the two [Iterable]s don't have the same length.
    */
   factory HashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
     HashMap<K, V> map = new HashMap<K, V>();
     Maps._fillMapWithIterables(map, keys, values);
     return map;
   }
 }