- this new module contains helpers to be able to receive connections
originated from a webextension context from a legacy extension context
(implemented by the `LegacyExtensionContext` class exported from
this new jsm module)
- two new test files (an xpcshell-test and a mochitest-browser) ensures that the LegacyExtensionContext can receive a Port
object and exchange messages with a background page and a content script (the content script test
is in a different test file because it doesn't currently work on android, because it needs
the browser.tabs API and the TabManager internal helper)
MozReview-Commit-ID: DS1NTXk0fB6
--HG--
extra : rebase_source : 462d6a461167e317297d204e72c2f6773bc5c770
9226a7b2f4
