Stephen: can you take this because you know the bot duration best? I tried to use ./tools/perf/generate_perf_sharding but it reshuffle all the existing benchmarks schedule :-/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/77e00452cac14a40ada774cd87bc25b3b4ee7ad8

commit 77e00452cac14a40ada774cd87bc25b3b4ee7ad8
Author: Stephen Martinis <martiniss@chromium.org>
Date: Sat Jul 01 01:09:12 2017

//tools/perf: Schedule speedometer on the waterfall

Bug:  734061 
Change-Id: I4be8f3ad317c0740740e9edfb7b8d7c13aa14c2c
Reviewed-on: https://chromium-review.googlesource.com/557994
Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#483885}
[modify] https://crrev.com/77e00452cac14a40ada774cd87bc25b3b4ee7ad8/testing/buildbot/chromium.perf.fyi.json
[modify] https://crrev.com/77e00452cac14a40ada774cd87bc25b3b4ee7ad8/testing/buildbot/chromium.perf.json
[modify] https://crrev.com/77e00452cac14a40ada774cd87bc25b3b4ee7ad8/tools/perf/benchmarks/speedometer2.py
[modify] https://crrev.com/77e00452cac14a40ada774cd87bc25b3b4ee7ad8/tools/perf/core/benchmark_sharding_map.json
[modify] https://crrev.com/77e00452cac14a40ada774cd87bc25b3b4ee7ad8/tools/perf/core/desktop_benchmark_avg_times.json