1443182 - Investigate NOT emitting ready / destroyed event in panels

Status: NEW

(DevTools :: Framework, enhancement, P3)

Description

[Nicolas Chevobbe [:nchevobbe]]

It looks like almost all panel emit `ready` [1] / `destroyed` [2] events, but it's unclear if they actually are of any use.
Let's see if they are, and if not, remove them.


[1] https://searchfox.org/mozilla-central/search?q=emit(%22ready%22&case=false&regexp=false&path=devtools%2Fclient
[2] https://searchfox.org/mozilla-central/search?q=emit(%22destroyed%22&case=false&regexp=false&path=devtools%2Fclient

Comment 1

[Alexandre Poirot [:ochameau]]

I imagine `ready` has been replaced by these events:
  https://searchfox.org/mozilla-central/source/devtools/client/framework/toolbox.js#1756-1757
But there isn't direct equivalent to `destroyed` ones, there are these, but it is fired just before we start destroying the panels
  https://searchfox.org/mozilla-central/source/devtools/client/framework/toolbox.js#2731-2732
  (We may emit `${panelId}-destroyed` events from toolbox.js when `panel.destroy()` returned promise resolves?)

`ready` events seems unused, but a couple of `destroyed` still are:
  https://searchfox.org/mozilla-central/search?q=.once(%22destroyed&case=false&regexp=false&path=
  Especially these occurrences:
    https://searchfox.org/mozilla-central/source/devtools/client/framework/toolbox-process-window.js#209
    https://searchfox.org/mozilla-central/source/devtools/client/netmonitor/test/head.js#327
    https://searchfox.org/mozilla-central/source/devtools/client/netmonitor/test/head.js#344


This bug report also highlights some other potential cleanups we could do now that there is no more xul addons:
* EventEmitter interface on panels is forced from toolbox, it looks hacky, it would be clear if all panels explicitely implement this interface
  https://searchfox.org/mozilla-central/rev/c217fbde244344fedfd07b57a740c694a456dbca/devtools/client/framework/toolbox.js#1721-1728
  https://searchfox.org/mozilla-central/rev/c217fbde244344fedfd07b57a740c694a456dbca/devtools/client/framework/toolbox.js#1748-1754
* All panels most likely all have an `open` method, so there is propably dead piece of code here:
  https://searchfox.org/mozilla-central/rev/c217fbde244344fedfd07b57a740c694a456dbca/devtools/client/framework/toolbox.js#1733-1742