1599353 - Provide a UI to enable Reflow logging

Status: NEW

(DevTools :: Console, enhancement, P3)

Description

[:Harald Kirschner :digitarald]

Reflow logs are useful to know which scripts change layout (vs touching the DOM), especially expensive/frequent layouts. DevTools still has the code but lost the UI during Console rewrite (afaik UI landed in bug 926371, backend in 453650).

Options, which could be combined:

1. Reflow option in Console's new overflow settings
2. Expose in Inspector (with highlighter)
3. Integrated with Event Listener Breakpoints. Unsure, as the actor probably doesn't provide pausable state and only synchronous layouts would be pausable. This would be bug 821829.

Reflow logs seem to show capture the duration and cause. It would be great if they could show the element.

Original release: https://hacks.mozilla.org/2013/11/firefox-developer-tools-episode-27-edit-as-html-codemirror-more/
Actor: https://searchfox.org/mozilla-central/source/devtools/server/actors/reflow.js