Remove the externallyForced method of DeviceImpl. It can be inferred from the presence of an owning display. BUG=742034 Change-Id: I6a33378f4256733da6d9658d47763153e431ad70 Reviewed-on: https://chromium-review.googlesource.com/854625 Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>