fix doc comments in dart:io and collection types

sdk/lib/collection/splay_tree.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;
 
 typedef bool _Predicate<T>(T value);
 
 /**
  * A node in a splay tree. It holds the sorting key and the left
@@ skipping 747 matching lines @@
     return _last.key;
   }
 
   E get single {
     if (_count == 0) throw IterableElementError.noElement();
     if (_count > 1) throw IterableElementError.tooMany();
     return _root.key;
   }
 
   // From Set.
-  bool contains(Object object) {
-    return _validKey(object) && _splay(object as dynamic/*=E*/) == 0;
+  bool contains(Object element) {
+    return _validKey(element) && _splay(element as dynamic/*=E*/) == 0;
   }
 
   bool add(E element) {
     int compare = _splay(element);
     if (compare == 0) return false;
     _addNewRoot(new _SplayTreeNode(element), compare);
     return true;
   }
 
   bool remove(Object object) {
@@ skipping 82 matching lines @@
   }
 
   void clear() {
     _clear();
   }
 
   Set<E> toSet() => _clone();
 
   String toString() => IterableBase.iterableToFullString(this, '{', '}');
 }