Follow up work from bug 1451159. This will move xpcshell preferences into the new testing/profiles system.

I was looking into this briefly, and xpcshell doesn't even use mozprofile. I guess the xpcshell binary doesn't read profile directories like Firefox does, so there's nothing to do here.

We want to run xpcshell with a special pref in bug 1470266. Normally this would be done by defining a special variable in the xpcshell command that head.js would then use to call Services.prefs.setCharPref(...). However, this adds more and more logic to head.js every time we have to do something like this. Let's pass in a prefs file via the xpcshell command line instead and set everything in that file. This will allow us to define prefs in `testing/profiles/xpcshell` instead of hardcoding them in head.js. I'll also implement a --setpref option.

If something goes wrong when setting prefs, that's something we'll want to know about as it likely means some tests will start to fail.

The current command line building is hard to follow and make sense of. Let's just use a single command variable and comment the order it needs. Depends on D9549

Pushed by ahalberstadt@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/ab0947533e9a [xpcshell] Stop ignoring failures in head.js when setting prefs, r=ted https://hg.mozilla.org/integration/autoland/rev/9688858bc5da [xpcshell] Cleanup code to build the xpcshell command, r=ted

Filed a follow-up to further simplify the command logic, bug 1501669.

This uses nsIPrefService.readUserPrefsFromFile to set preferences from a user.js passed in via the python harness. This allows us to use the profiles under testing/profiles like all the other harnesses and will make setting prefs in xpcshell easier to use and understand.

This commit creates an empty 'base' profile because I wanted to preserve the ability to apply a pref to all test harnesses on try. Since xpcshell doesn't share many prefs with the other harnesses, it can't use the common profile. So adding a pref to 'common' will apply it everywhere except xpcshell. Adding a pref to 'base' will apply it everywhere including xpcshell. These profiles are starting to get a bit messy, but I'd like to punt re-organizing them to a follow-up bug. Depends on D9716

Here's the latest two commits on try: https://treeherder.mozilla.org/#/jobs?repo=try&author=ahalberstadt%40mozilla.com&tochange=074245a38eac0190f49ffaba13b7afd1ba75357c&fromchange=294b09383bddf0ffb1aaebefd849e8707c3c27dc (Android bustage fixed in second push)

https://hg.mozilla.org/mozilla-central/rev/ab0947533e9a https://hg.mozilla.org/mozilla-central/rev/9688858bc5da

Parsing prefs and env on the command line is a common task performed by our harnesses, let's move it into mozbase. Depends on D9717

Depends on D9796

Fyi that is the last of the patches in this series. Here's a new try run with 3 retriggers for each task: https://treeherder.mozilla.org/#/jobs?repo=try&revision=8593dbe58db2a9762a376823f100cacd4c817522 The Win10 xpcshell tasks (especially opt) fail very frequently on mozilla-central, so I expect a bunch of orange there.

Not sure what those Android build bustages are, but I can't see how they'd be related to this patch.

Pushed by ahalberstadt@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/9e438c55a248 [xpcshell] Use nsIPrefService.readUserPrefsFromFile to set prefs, r=ted https://hg.mozilla.org/integration/autoland/rev/a2161aab4e4e [xpcshell] Define preferences in testing/profiles instead of testing/xpcshell/head.js, r=ted

Backed out 2 changesets (bug 1460914)for multiple failures on profile_data/base "CLOSED TREE" Backout revision:https://hg.mozilla.org/integration/autoland/rev/ba1fcb7618efc99f927339eb10e818aaebbe11bf Failed push:https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception&classifiedState=unclassified&selectedJob=208036560&revision=a2161aab4e4ed8cf7cf69c1fc281e87915a561da Failure log: https://treeherder.mozilla.org/logviewer.html#?job_id=208036532&repo=autoland https://treeherder.mozilla.org/logviewer.html#?job_id=208034918&repo=autoland :ahal Could you please take a look?

Oops, forgot to add "base/*" to the profile_files list in testing/profiles/moz.build. Xpcshell didn't fail because it gets packaged from the srcdir anyway (mochitest, reftest, et al grab it from the objdir). I'll file a follow-up bug so stop copying testing/profiles to the objdir. Like :ted mentioned in one of his review comments, when running locally harnesses should just be able to find it in the srcdir, and in CI we can copy it to the test archive straight from the srcdir as well. We should also archive them in a single place in tests.common.zip so we aren't uploading/downloading these files multiple times.

Fixed: https://treeherder.mozilla.org/#/jobs?repo=try&revision=0d3635e520379e13c5299a09cc38beab8deb56db

Pushed by ahalberstadt@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/1ba93cd55330 [xpcshell] Use nsIPrefService.readUserPrefsFromFile to set prefs, r=ted https://hg.mozilla.org/integration/autoland/rev/20a550cfc08f [xpcshell] Define preferences in testing/profiles instead of testing/xpcshell/head.js, r=ted

https://hg.mozilla.org/mozilla-central/rev/1ba93cd55330 https://hg.mozilla.org/mozilla-central/rev/20a550cfc08f

Pushed by ahalberstadt@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/f99b45112279 [mozprofile] Move mochitest's 'parseKeyValue' function into mozprofile.cli, r=ted https://hg.mozilla.org/integration/autoland/rev/531299c96e09 [xpcshell] Add --setpref to the command line, r=ted

https://hg.mozilla.org/mozilla-central/rev/f99b45112279 https://hg.mozilla.org/mozilla-central/rev/531299c96e09