1425587 - Investigate avoiding creating about:blank content viewers that we then throw away

Status: NEW

(Firefox :: General, enhancement, P3)

Description

[:Gijs (he/him)]

This came up in bug 1425466, but also seems like it's quite related to bug 1397365 (though I could be wrong!). :kmag, did you have specific culprits in mind in bug 1425466 comment 9 where we can avoid creating about:blank ?

Comment 1

[Florian Quèze [:florian]]

Attachment: dump about:blank stacks

This is a diagnosis patch I used to figure out what is triggering it. It seems to be the _securityUI getter in browser.xml that creates about:blank documents in the main browser window.

Comment 2

[Kris Maglione [:kmag]]

I'm not sure about specific culprits, but I came across this in a lot of places when I was investigating certain WebExtension performance issues. In the profiles, our code creates a docShell, then some other frame script or process script code with an observer causes a document viewer to be instantiated, which triggers a bunch of other observers, before we blow all of it away. WebExtensions code was probably also a culprit in a lot of cases, before we migrated our content script tracking code to C++.

This turns up in fairly obvious ways in content process startup profiles, so it shouldn't be hard to narrow down.