1754452 - Instantiate WebExtension top level target from the server side -- support server side target switching for webext

Status: ASSIGNED

(DevTools :: Framework, task)

Description

[Alexandre Poirot [:ochameau]]

Bug 1675456 added the minimal support for the watcher actor to debug web extension.
The main goal was to support watching for resources on the server side so that we could drop legacy resource watcher.
But there is one thing left to complete the migration to JSWindowActor and embrace the full support of the watcher actor.
We should support "server side target switching".
It means that all targets should be spawn by the server, including the top level one. It means that the WebExtensionTarget should be spawn by the server instead of the client.
While doing that, we might also apply the "every frame target" pattern to web extension. Intead of having one magical target debugging many documents, we would spawn one target per document.

Comment 1

[Alexandre Poirot [:ochameau]]

Attachment: Bug 1754452 - [devtools] Spawn many target actor for WebExtension - EFT and server targets for WebExtensions.

Comment 2

[Alexandre Poirot [:ochameau]]

Comment on attachment 9271795 [details]
Bug 1754452 - [devtools] Spawn many target actor for WebExtension - EFT and server targets for WebExtensions.

This patch is actually only 50% of the work.
It enables "Server side target switching" (and may be also EFT?) for the TabDescriptor spawn by WebExt codebase.

But another patch is necessary also against the WebExtensionDescriptor, to address this other disable of server side target switching:
https://searchfox.org/mozilla-central/rev/6da1ebe13b260efabd88eb98dec5fa8ee65987b2/devtools/client/fronts/descriptors/webextension.js#99-115
(which also relates to EFT)