The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f656862394e0006712f3d3427b5d58f4191c3469

commit f656862394e0006712f3d3427b5d58f4191c3469
Author: Kenneth Russell <kbr@chromium.org>
Date: Mon Aug 14 22:45:16 2017

Shard webgl_conformance_tests on Android.

This will only have an effect on the Nexus 5X bots, which are the only
ones Swarmed right now. They're sharded 6 ways to try to get the
per-shard runtime down to 5 minutes. It may be necessary to follow
this up with a CL that adds per-test runtimes, in the same way done
for the WebGL 2.0 conformance tests.

BUG= 754467 
TBR=ynovikov@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Iaa8c63bebe6f517c02a62de93e52e218ef93f893
Reviewed-on: https://chromium-review.googlesource.com/612697
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#494221}
[modify] https://crrev.com/f656862394e0006712f3d3427b5d58f4191c3469/content/test/gpu/generate_buildbot_json.py
[modify] https://crrev.com/f656862394e0006712f3d3427b5d58f4191c3469/testing/buildbot/chromium.gpu.fyi.json
[modify] https://crrev.com/f656862394e0006712f3d3427b5d58f4191c3469/testing/buildbot/client.v8.fyi.json

We definitely need to use the per-test times to get a better shard distribution. Right now one of the shards takes 19 minutes and the others take 4 minutes or less.

https://luci-milo.appspot.com/buildbot/chromium.gpu.fyi/Android%20Release%20%28Nexus%205X%29/9900

The test times in the forthcoming CL were gathered via:

python gather_swarming_json_results.py --waterfall chromium.gpu.fyi --bot "Android Release (Nexus 5X)" --build 9948 --step webgl_conformance_tests --output webgl_conformance_tests_output.json

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/acf059f108c127f38f0234df97c4268869dfb507

commit acf059f108c127f38f0234df97c4268869dfb507
Author: Kenneth Russell <kbr@chromium.org>
Date: Thu Aug 17 19:18:53 2017

Use test runtimes to distribute shards more evenly on Android.

Updated the gather_swarming_json_results.py script to work with the
new luci-milo prpc endpoints rather than the BuildBot JSON endpoints,
which have been decommissioned.

BUG= 754467 
TBR=ynovikov@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I9397efbc337acee217b75a5cc94128aa0a581bfc
Reviewed-on: https://chromium-review.googlesource.com/618299
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495271}
[add] https://crrev.com/acf059f108c127f38f0234df97c4268869dfb507/content/test/data/gpu/webgl_conformance_tests_output.json
[modify] https://crrev.com/acf059f108c127f38f0234df97c4268869dfb507/content/test/gpu/gather_swarming_json_results.py
[modify] https://crrev.com/acf059f108c127f38f0234df97c4268869dfb507/content/test/gpu/generate_buildbot_json.py
[modify] https://crrev.com/acf059f108c127f38f0234df97c4268869dfb507/testing/buildbot/chromium.gpu.fyi.json
[modify] https://crrev.com/acf059f108c127f38f0234df97c4268869dfb507/testing/buildbot/client.v8.fyi.json

From https://luci-milo.appspot.com/buildbot/chromium.gpu.fyi/Android%20Release%20%28Nexus%205X%29/9970 and examining the run time of the shards, they were evenly distributed, around 6-7 minutes each.