Introduce per-tab preferences service.

chrome/browser/prefs/per_tab_user_pref_store.cc

Index: chrome/browser/prefs/per_tab_user_pref_store.cc
diff --git a/chrome/browser/prefs/per_tab_user_pref_store.cc b/chrome/browser/prefs/per_tab_user_pref_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1de2c752d5afaddce72c47f049d693bb5dd9cc3a
--- /dev/null
+++ b/chrome/browser/prefs/per_tab_user_pref_store.cc
@@ -0,0 +1,9 @@
+// Copyright (c) 2011 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 "chrome/browser/prefs/per_tab_user_pref_store.h"
+
+PerTabUserPrefStore::PerTabUserPrefStore(PersistentPrefStore* underlay)
+    : OverlayUserPrefStore(underlay) {
+}