Checks compare stable v. experimental baseline

[gsnedders]

e.g. https://github.com/web-platform-tests/wpt/runs/40189217:

this shows:

Run	Spec
master	chrome-72.0.3626.14 dev-linux-18.04@9bf305b4ed
48d5d50	chrome-71.0.3578.80-linux-18.04@48d5d5033d

The comparison of Chrome 72 v. Chrome 71 seems bogus.

And the chrome[experimental] run (https://github.com/web-platform-tests/wpt/runs/40181992) shows the equally bogus:

Run	Spec
master	chrome-71.0.3578.80-linux-18.04@48d5d5033d
48d5d50	chrome-72.0.3626.14 dev-linux-18.04@48d5d5033d

[lukebjerring]

Fairly sure this will be fixed by #889 which plumbs the experimental label through to the GetDiffURL command.

[Hexcles]

@lukebjerring no, that's a separate issue. IIUC, GetDiffURL is only responsible for generating the link, not for finding the runs. I think the problem here is that we need to pass the labels from the receiver to ScheduleResultsProcessing.

[lukebjerring]

OK, this was introduced in #881, and I've amended #889 to indeed fix the problem.

[Hexcles]

Should be fixed now.