This commit make it possible the creation of hybrid addons as part of the set of
SDK test addons.
Unfortunately these SDK test addons are build using the old cfx tool and the its
related module loader, and so this patch applies the changes needed to:
- optionally include an `hasEmbeddedWebExtension` option in the generated "install.rdf"
(if the test addon "package.json" contains a property with the same name
in its "package.json")
- initialize the "sdk/webextension" from the bootstrap method params
(as already done in the previous patch for the new SDK module loader)
- include the "webextension/" dir in the generated xpi, if any (similarly
to how it is already done for the "chrome/" dir, which an SDK addon can optionally
contain)
MozReview-Commit-ID: 4WS5ZYkl8FY
