Add variant handling to performance tests.

BUG=chromium:454915
TEST=Unit test for perf_uploader, ran network_WiFi_Perf

Change-Id: I9718b340fced30756d6b7f015e3a7945b1aa4f45
Reviewed-on: https://chromium-review.googlesource.com/246310
Tested-by: Kris Rambish <krisr@chromium.org>
Reviewed-by: Bindu Mahadev <bmahadev@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Kris Rambish <krisr@chromium.org>
4 files changed