[Doodle] Cache the DoodleConfig in prefs

components/doodle/pref_names.h

Index: components/doodle/pref_names.h
diff --git a/components/doodle/pref_names.h b/components/doodle/pref_names.h
new file mode 100644
index 0000000000000000000000000000000000000000..20d7b061a1a628eedad4f0912eb51c6cd10967ca
--- /dev/null
+++ b/components/doodle/pref_names.h
@@ -0,0 +1,17 @@
+// 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.
+
+#ifndef COMPONENTS_DOODLE_PREF_NAMES_H_
+#define COMPONENTS_DOODLE_PREF_NAMES_H_
+
+namespace doodle {
+namespace prefs {
+
+extern const char kCachedConfig[];
+extern const char kCachedConfigExpiry[];
+
+}  // namespace prefs
+}  // namespace doodle
+
+#endif  // COMPONENTS_DOODLE_PREF_NAMES_H_