Add fromIterable(s) constructors in SplayTreeMap and LinkedHashMap.

sdk/lib/collection/maps.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.collection;
 
 /*
  * Helper class which implements complex [Map] operations
  * in term of basic ones ([Map.keys], [Map.operator []],
  * [Map.operator []=] and [Map.remove].)  Not all methods are
@@ skipping 59 matching lines @@
    * directly as a key or value, or indirectly through other collections
    * or maps, the contained reference is rendered as [:'{...}':]. This
    * prevents the infinite regress that would otherwise occur. So, for example,
    * calling this method on a map whose sole entry maps the string key 'me'
    * to a reference to the map would return [:'{me: {...}}':].
    *
    * A typical implementation of a map's [toString] method will
    * simply return the results of this method applied to the collection.
    */
   static String mapToString(Map m) => ToString.mapToString(m);
+
+  static _id(x) => x;
+
+  /**
+   * Fills a map with key/value pairs computed from [iterable].
+   *
+   * This method is used by Map classes in the named constructor fromIterable.
+   */
+  static void _fillMapWithMappedIterable(Map map, Iterable iterable,
+                                         key(element), value(element)) {
+    if (key == null) key = _id;
+    if (value == null) value = _id;
+
+    for (var element in iterable) {
+      map[key(element)] = value(element);
+    }
+  }
+
+  /**
+   * Fills a map by associating the [keys] to [values].
+   *
+   * This method is used by Map classes in the named constructor fromIterables.
+   */
+  static void _fillMapWithIterables(Map map, Iterable keys,
+                                    Iterable values) {
+    Iterator keyIterator = keys.iterator;
+    Iterator valueIterator = values.iterator;
+
+    bool hasNextKey = keyIterator.moveNext();
+    bool hasNextValue = valueIterator.moveNext();
+
+    while (hasNextKey && hasNextValue) {
+      map[keyIterator.current] = valueIterator.current;
+      hasNextKey = keyIterator.moveNext();
+      hasNextValue = valueIterator.moveNext();
+    }
+
+    if (hasNextKey || hasNextValue) {
+      throw new ArgumentError("Iterables do not have same length.");
+    }
+  }
 }