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 ?
Created attachment 8937192 [details] [diff] [review] 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.
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.
Priority: -- → P3
You need to log in before you can comment on or make changes to this bug.