[IndexedDB] Adding transaction and value support to observers

content/browser/indexed_db/list_set.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_INDEXED_DB_LIST_SET_H_
 #define CONTENT_BROWSER_INDEXED_DB_LIST_SET_H_
 
 #include <stddef.h>
 
 #include <algorithm>
@@ skipping 15 matching lines @@
 class list_set {
  public:
   list_set() {}
   list_set(const list_set<T>& other) : list_(other.list_), set_(other.set_) {}
   list_set& operator=(const list_set<T>& other) {
     list_ = other.list_;
     set_ = other.set_;
     return *this;
   }
 
+  void insert_front(const T& elem) {
+    if (set_.find(elem) != set_.end())
+      return;
+    set_.insert(elem);
+    list_.push_front(elem);
+  }
+
   void insert(const T& elem) {
     if (set_.find(elem) != set_.end())
       return;
     set_.insert(elem);
     list_.push_back(elem);
   }
 
   void erase(const T& elem) {
     if (set_.find(elem) == set_.end())
       return;
@@ skipping 107 matching lines @@
   std::set<T> set_;
 };
 
 // Prevent instantiation of list_set<std::unique_ptr<T>> as the current
 // implementation would fail.
 // TODO(jsbell): Support scoped_ptr through specialization.
 template <typename T>
 class list_set<std::unique_ptr<T>>;
 
 #endif  // CONTENT_BROWSER_INDEXED_DB_LIST_SET_H_