Add Sync datatype for shared managed user settings.

sync/internal_api/write_node.cc

Index: sync/internal_api/write_node.cc
diff --git a/sync/internal_api/write_node.cc b/sync/internal_api/write_node.cc
index 079987af3a469b13837c2af3b2ea37d1a9efec8c..6062704d2155a47f999cce82c07ec71e39b1b0a4 100644
--- a/sync/internal_api/write_node.cc
+++ b/sync/internal_api/write_node.cc
@@ -200,6 +200,13 @@ void WriteNode::SetManagedUserSpecifics(
   SetEntitySpecifics(entity_specifics);
 }
 
+void WriteNode::SetManagedUserSharedSettingSpecifics(
+    const sync_pb::ManagedUserSharedSettingSpecifics& new_value) {
+  sync_pb::EntitySpecifics entity_specifics;
+  entity_specifics.mutable_managed_user_shared_setting()->CopyFrom(new_value);
+  SetEntitySpecifics(entity_specifics);
+}
+
 void WriteNode::SetDeviceInfoSpecifics(
     const sync_pb::DeviceInfoSpecifics& new_value) {
   sync_pb::EntitySpecifics entity_specifics;