Code review comment for lp://staging/~knitzsche/scope-aggregator/refactor-handle-methods_add-login_remove-shared-category

Note: I started doing this refactoring to help debug https://bugs.launchpad.net/canonical-devices-system-image/+bug/1622423. However, after the refactor that issue continues, and I suspect it may be a unity8 rendering issue (I am working with unity api team on this separately).