Move Iterable implementation to collection.

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;
 
 /**
  * The String class represents sequences of characters. Strings are
  * immutable. A string is represented by a sequence of Unicode UTF-16
  * code units accessible through the [codeUnitAt] or the
@@ skipping 233 matching lines @@
    * If this string is not already all upper case, returns a new string
    * where all characters are made upper case. Returns [:this:] otherwise.
    */
   // TODO(floitsch): document better. (See EcmaScript for description).
   String toUpperCase();
 }
 
 /**
  * The runes (integer Unicode code points) of a [String].
  */
-class Runes extends Iterable<int> {
+class Runes extends IterableBase<int> {
   final String string;
   Runes(this.string);
 
   RuneIterator get iterator => new RuneIterator(string);
 
   int get last {
     if (string.length == 0) {
       throw new StateError("No elements.");
     }
     int length = string.length;
@@ skipping 174 matching lines @@
         _position = position - 1;
         _currentCodePoint = _combineSurrogatePair(prevCodeUnit, codeUnit);
         return true;
       }
     }
     _position = position;
     _currentCodePoint = codeUnit;
     return true;
   }
 }