Bugzilla

(In reply to Nika Layzell [:nika] (ni? for response) from comment #13)
> I think we want to continue blocking disabling e10s on shipped builds, even if they set the environment variable. non-e10s is known to be quite a broken & insecure configuration, and we have basically no tests for it.
> 
> In terms of using non-e10s for testing & local development, I'm a bit more uncertain. Doing this is a thing which I certainly used to do all of the time, but haven't reached for as a tool in quite a while. I suppose I'm not inherently opposed to having a difficult-to-enable-for-an-actual-user mechanism for turning e10s off for testing, but I don't feel strongly that it's something we need to introduce, and I don't want it available on shipping builds. Theoretically a dev could modify the `BrowserTabsRemoteAutostart` function and re-build (it should be relatively fast) if they really need to enable non-e10s for some local testing, though I expect it to break even more over time.

How about we allow `MOZ_FORCE_DISABLE_E10S` to apply if `MOZILLA_OFFICIAL` is unset? We already use this to enable additional developer things in the main menu for developers and it works for local builds (artifact or full). But it wouldn't work for Nightly, Beta and Release builds.

(In reply to Nika Layzell [:nika] (ni? for response) from comment #13)
> I think we want to continue blocking disabling e10s on shipped builds, even if they set the environment variable. non-e10s is known to be quite a broken & insecure configuration, and we have basically no tests for it.
> 
> In terms of using non-e10s for testing & local development, I'm a bit more uncertain. Doing this is a thing which I certainly used to do all of the time, but haven't reached for as a tool in quite a while. I suppose I'm not inherently opposed to having a difficult-to-enable-for-an-actual-user mechanism for turning e10s off for testing, but I don't feel strongly that it's something we need to introduce, and I don't want it available on shipping builds. Theoretically a dev could modify the `BrowserTabsRemoteAutostart` function and re-build (it should be relatively fast) if they really need to enable non-e10s for some local testing, though I expect it to break even more over time.

How about we allow `MOZ_FORCE_DISABLE_E10S` to apply if `MOZILLA_OFFICIAL` is unset? We already use this to [enable additional developer things](https://searchfox.org/mozilla-central/rev/04f7743d94691fa24212fb43099f9d84c3bfc890/browser/base/content/browser.js#1953-1955) in the main menu for developers and it works for local builds (artifact or full). But it wouldn't work for Nightly, Beta and Release builds.