diff -r 000000000000 -r 6474c204b198 ipc/chromium/src/base/revocable_store.cc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ipc/chromium/src/base/revocable_store.cc	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,47 @@
+// Copyright (c) 2006-2008 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.
+
+#include "base/revocable_store.h"
+
+#include "base/logging.h"
+
+RevocableStore::Revocable::Revocable(RevocableStore* store)
+    : store_reference_(store->owning_reference_) {
+  // We AddRef() the owning reference.
+  DCHECK(store_reference_->store());
+  store_reference_->store()->Add(this);
+}
+
+RevocableStore::Revocable::~Revocable() {
+  if (!revoked()) {
+    // Notify the store of our destruction.
+    --(store_reference_->store()->count_);
+  }
+}
+
+RevocableStore::RevocableStore() : count_(0) {
+  // Create a new owning reference.
+  owning_reference_ = new StoreRef(this);
+}
+
+RevocableStore::~RevocableStore() {
+  // Revoke all the items in the store.
+  owning_reference_->set_store(NULL);
+}
+
+void RevocableStore::Add(Revocable* item) {
+  DCHECK(!item->revoked());
+  ++count_;
+}
+
+void RevocableStore::RevokeAll() {
+  // We revoke all the existing items in the store and reset our count.
+  owning_reference_->set_store(NULL);
+  count_ = 0;
+
+  // Then we create a new owning reference for new items that get added.
+  // This Release()s the old owning reference, allowing it to be freed after
+  // all the items that were in the store are eventually destroyed.
+  owning_reference_ = new StoreRef(this);
+}