Chrome Version: ToT
OS: ChromeOS

This is a tracking bug for internal clean up.
Currently ArcService classes are instantiated regardless of whether the device supports ARC or not.
cf) https://cs.chromium.org/chromium/src/chrome/browser/chromeos/arc/arc_service_launcher.cc?sq=package:chromium&dr=CSs&rcl=1485491011&l=76

We may want not to instantiated if ARC is supported on the device, because these just would be unnecessarily.
From programming point of view, always instantiating the class reduces the cases we need to think about, and setting up browser test fixture would be slightly simpler.