[Doodle] Make DoodleService a KeyedService and add a factory

components/doodle/doodle_service.cc

Index: components/doodle/doodle_service.cc
diff --git a/components/doodle/doodle_service.cc b/components/doodle/doodle_service.cc
index ae37a8613b121646c4ab4815bf1f064ea8e52133..12a56200bb613a7a9dae0f583c444d2082489220 100644
--- a/components/doodle/doodle_service.cc
+++ b/components/doodle/doodle_service.cc
@@ -47,6 +47,8 @@ DoodleService::DoodleService(PrefService* pref_service,
 
 DoodleService::~DoodleService() = default;
 
+void DoodleService::Shutdown() {}
+
 void DoodleService::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }