[Doodle] Cache the DoodleConfig in prefs

components/doodle/pref_names.cc

Index: components/doodle/pref_names.cc
diff --git a/components/doodle/pref_names.cc b/components/doodle/pref_names.cc
new file mode 100644
index 0000000000000000000000000000000000000000..17ff266090e43b45f61a0f86774bdc66a6427997
--- /dev/null
+++ b/components/doodle/pref_names.cc
@@ -0,0 +1,14 @@
+// Copyright 2017 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 "components/doodle/pref_names.h"
+
+namespace doodle {
+namespace prefs {
+
+const char kCachedConfig[] = "doodle.cached_config";
+const char kCachedConfigExpiry[] = "doodle.cached_config_expiry";
+
+}  // namespace prefs
+}  // namespace doodle