Addons can be installed and uninstalled using the Marionette client
utility found in testing/marionette/client/marionette_driver/addons.py.
It injects system-privileged chrome JavaScript to manipulate the addon
manager service.
To make this feature more widely adopted, i.e. by other clients such as
WebDriver, this patch moves the addon installation code to internally
in Marionette and exposes them as so called WebDriver extension commands.
This patch also _explicitly breaks_ backwards compatibility with
older Geckos that do not support the new Marionette:installAddon and
Marionette:uninstallAddon commands.
MozReview-Commit-ID: 18IceiGIg5H
--HG--
extra : rebase_source : 007802fa0a431a1438570caac3988177c6beab1d
Thomas Charles
Andreas Tolfsen