As things are now, getting WebExtensions API into your extension requires something like the following: let extension = new Extension(...); extension.startup().then(function() { let context = new ExtensionPage(extension, {type: "background", contentWindow: global}); let chrome = Management.generateAPIs(extension, context); ... } Problem is: neither ExtensionPage nor Management are public API. Also, it's not obvious whether omitting docShell parameter (which is not available in many contexts) will have consequences. There really should be a simple and public shortcut to generate the APIs, for example: let chrome = extension.generateAPIs(global);

I don't think I agree with the dupe here. native.js is intended to be for new APIs that could be used by a variety of add-ons. Perhaps we could use some of the same code to allow regular extensions to use WebExtension APIs. But I want to make sure that the concepts of "native.js extension" and "legacy extension with some WebExtension code attached" are kept pretty separate. So I could see the native.js prototype being a dependency here, but not a dupe.

Fair enough, as long as we're clear that this is about allowing traditional extensions to provide APIs for code running in that extension, and not about allowing them to provide APIs for other extensions.

Yes, this is about traditional extensions using APIs provided by WebExtensions - as a way to transition to WebExtensions gradually. Bug 1215035 has an explanation why this gradual transition is necessary.

I think based on https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Embedded_WebExtensions, that we can now close this one.