Add a scoped notifier for pref dictionaries / lists.

chrome/browser/scoped_pref_update.cc

Index: chrome/browser/scoped_pref_update.cc
diff --git a/chrome/browser/scoped_pref_update.cc b/chrome/browser/scoped_pref_update.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1a73466b127210d71431c9ca6039d3706bbba3f2
--- /dev/null
+++ b/chrome/browser/scoped_pref_update.cc
@@ -0,0 +1,15 @@
+// Copyright (c) 2010 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/values.h"
+#include "chrome/browser/pref_service.h"
+#include "chrome/browser/scoped_pref_update.h"
+
+ScopedPrefUpdate::ScopedPrefUpdate(PrefService* service, const wchar_t* path)
+    : service_(service),
+      path_(path) {}
+
+ScopedPrefUpdate::~ScopedPrefUpdate() {
+  service_->FireObservers(path_.c_str());
+}