Valgrind experiment

I don't really expect this to fix the errors, but I think
it's worth it to try shaking up the valgrind bot overnight.
There's some strange behavior with regard to color type on
the valgrind bot that I can't reproduce and that we aren't
seeing on any of the other bots.

TBR=mtklein,scroggo

BUG=skia:

Review URL: https://codereview.chromium.org/1418723002
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