1951773 - Add documentation for initialization/ uninitialization of various components / observers via BrowserComponents.manifest

Status: NEW

(Firefox :: General, task, P3)

Description

[Mike Conley (:mconley) (:⚙️)]

In bug 1949898, and elsewhere in bug 1896783 and bug 1880904, we've started to change the idiom we use for component initialization. The old pattern was to use BrowserGlue or browser-init / browser.js as a dumping ground for module imports and initialization routines. With the mentioned bugs and their dependencies landed / landing, we've got a new technique here where modules can be registered to initialize / uninitialize statically in BrowserComponents.manifest.

We should add some documentation to make it clear how this works, what the various points in time are that the modules can be registered for, potential gotchas (like how module initialization exceptions get automatically caught), etc.