sync: Add ControlPreference protobuf and supporting code

sync/protocol/proto_value_conversions.h

Index: sync/protocol/proto_value_conversions.h
diff --git a/sync/protocol/proto_value_conversions.h b/sync/protocol/proto_value_conversions.h
index 5c150ceee0865fe762c8e31c40f72589c2e7289c..a996f6ef91f154206eafba3a14329926b1af4e94 100644
--- a/sync/protocol/proto_value_conversions.h
+++ b/sync/protocol/proto_value_conversions.h
@@ -23,6 +23,7 @@ class AutofillSpecifics;
 class BookmarkSpecifics;
 class ClientToServerMessage;
 class ClientToServerResponse;
+class ControlPreferenceSpecifics;
 class DatatypeAssociationStats;
 class DebugEventInfo;
 class DebugInfo;
@@ -140,6 +141,9 @@ SYNC_EXPORT_PRIVATE base::DictionaryValue* DeviceInfoSpecificsToValue(
 SYNC_EXPORT_PRIVATE base::DictionaryValue* ExperimentsSpecificsToValue(
     const sync_pb::ExperimentsSpecifics& proto);
 
+SYNC_EXPORT_PRIVATE base::DictionaryValue* ControlPreferenceSpecificsToValue(
+    const sync_pb::ControlPreferenceSpecifics& proto);
+
 SYNC_EXPORT_PRIVATE base::DictionaryValue* ExtensionSettingSpecificsToValue(
     const sync_pb::ExtensionSettingSpecifics& extension_setting_specifics);