Adding RegisterDependantFieldTrial interface method.

components/sync/user_events/user_event_service.cc

Index: components/sync/user_events/user_event_service.cc
diff --git a/components/sync/user_events/user_event_service.cc b/components/sync/user_events/user_event_service.cc
index 328808b6dcbfd6d8fa9ed6eaf4a231e102f2633b..7a7e0b8cc58de5981de20c4ac054e3ff14475d9c 100644
--- a/components/sync/user_events/user_event_service.cc
+++ b/components/sync/user_events/user_event_service.cc
@@ -13,20 +13,19 @@
 #include "components/sync/driver/sync_driver_switches.h"
 #include "components/sync/driver/sync_service.h"
 #include "components/sync/model/model_type_sync_bridge.h"
-#include "components/sync/protocol/sync.pb.h"
 #include "components/sync/user_events/user_event_sync_bridge.h"
 
 using sync_pb::UserEventSpecifics;
 
 namespace syncer {
 
-namespace {}  // namespace
-
 UserEventService::UserEventService(SyncService* sync_service,
                                    std::unique_ptr<UserEventSyncBridge> bridge)
     : sync_service_(sync_service),
       bridge_(std::move(bridge)),
-      session_id_(base::RandUint64()) {}
+      session_id_(base::RandUint64()) {
+  // TODO(skym): Subscribe to events about field trial membership changing.
+}
 
 UserEventService::~UserEventService() {}
 
@@ -58,4 +57,9 @@ bool UserEventService::CanRecordEvent(const UserEventSpecifics& specifics) {
          sync_service_->GetPreferredDataTypes().Has(HISTORY_DELETE_DIRECTIVES);
 }
 
+void RegisterDependentFieldTrial(const std::string& trial_name,
+                                 UserEventSpecifics::EventCase event_case) {
+  // TODO(skym): Implementation.
+}
+
 }  // namespace syncer