Reland "Reland "Cleanup run_performance_tests.py's output files handling""

This is a reland of 76044ee0f02ea7016ae4754a55aeb665bfdc1df7

Patchset 1 is the original change.

Patchset 2 is the change with the flaky test disabled on Android for
crbug.com/932301

Original change's description:
> Reland "Cleanup run_performance_tests.py's output files handling"
>
> Relanding https://chromium-review.googlesource.com/c/1449151 with fixes.
>
> Patchset 1 is https://chromium-review.googlesource.com/c/1449151
>
> Patchset 2 is https://chromium-review.googlesource.com/c/1464228
>
> Patchset 3 is the new fix. When you run a telemetry benchmark as a
> reference, you are supposed to do
> `run_benchmark benchmark_name --browser=reference`
> but I thought that you were supposed to do
> `run_benchmark benchmark_name.reference --browser=reference`
> because I read the earlier code wrong.
> I also added a end to end test for this behavior, which also
> covers sharding code as well.
>
> Patchset 5 is a unittest for
> https://chromium-review.googlesource.com/c/1464228
>
> Bug: 930879, 928928, 927507, 923628, 920002, 744736
> Change-Id: If73d929b8e1b32c33d2bed7d2298b64d205658c1
> Reviewed-on: https://chromium-review.googlesource.com/c/1467907
> Reviewed-by: Emily Hanley <eyaich@chromium.org>
> Reviewed-by: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#632333}

Bug: 930879, 928928, 927507, 923628, 920002, 744736
Change-Id: I258acbee9ee47c48e8f872899bc1e21148366edb
Reviewed-on: https://chromium-review.googlesource.com/c/1474841
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632857}
3 files changed