Making QuantumRender tier-1

[Kartikaya Gupta]

(cross-posted to dev-tech-gfx and dev-tree-management, please direct
replies to dev-platform)

I just landed a change on inbound (bug 1363344) that enables various
test jobs (reftests, jsreftests, crashtests, webgl mochitests, gpu
mochitests) on the Linux64 QuantumRender (aka "linux64-qr") platform
for autoland, inbound, and central. It also marks them as tier-1, so
breaking these will probably result in backout of the offending patch.
We are making this change for a couple of reasons:

1) we've had a number of cases recently where after merging a pile of
stuff from m-c over to the graphics branch, we got QR test bustage,
and it was painful to track down what caused it
2) this is a necessary step for QR work to migrate from the graphics
to using the regular integration branches, which is something we'd
like to do in the not-too-distant future

If you do cause breakage in QR jobs, you should be able to reproduce
it locally or on try as with regular tests. A "linux64-qr" build is
just a regular linux64 build with the gfx.webrender.enabled pref set
to true. (I plan to eliminate the actual build job in bug 1342488). On
try you can use a syntax like "try: -b o -p linux64-qr -u
all[linux64-qr]" to run all the available linux64-qr tests.

Cheers,
kats