Increase swarming shards for some asan tests

viz_browser_tests, viz_content_browsertests and content_browsertest take more than 20 minutes on linux asan bot.
This patch increases the shard for such slow tests.
* viz_browser_tests, 10 -> 20: max shard duration become 14 mins from > 25 mins
* viz_content_browsertests, 2 -> 8: max shard duration become 15 mins from > 50 mins
* content_browsertests, 4 -> 8: max shard duration become 16 mins from > 25 mins

linux_chromium_asan_rel_ng has the slowest average CQ cycle time, so reducing test execution time is effective for overall CQ cycle time.
1 week stats of average cycle time of each try builder: http://shortn/_bEvlzGZaH9


Recent history of tests on linux_chromium_asan_rel_ng:
* viz_browser_tests
https://chromium-swarm.appspot.com/tasklist?c=name&c=state&c=created_ts&c=duration&c=pending_time&c=pool&c=bot&et=1528691160000&f=state%3ACOMPLETED_SUCCESS&f=name-tag%3Aviz_browser_tests&f=buildername-tag%3Alinux_chromium_asan_rel_ng&l=50&s=duration%3Adesc&st=1528604760000
* viz_content_browsertests
https://chromium-swarm.appspot.com/tasklist?c=name&c=state&c=created_ts&c=duration&c=pending_time&c=pool&c=bot&et=1528691160000&f=state%3ACOMPLETED_SUCCESS&f=buildername-tag%3Alinux_chromium_asan_rel_ng&f=name-tag%3Aviz_content_browsertests&l=50&s=duration%3Adesc&st=1528604760000
* content_browsertests
https://chromium-swarm.appspot.com/tasklist?c=name&c=state&c=created_ts&c=duration&c=pending_time&c=pool&c=bot&et=1528691160000&f=state%3ACOMPLETED_SUCCESS&f=buildername-tag%3Alinux_chromium_asan_rel_ng&f=name-tag%3Acontent_browsertests&l=50&s=duration%3Adesc&st=1528604760000

Bug: 794372
Change-Id: Ic5a4daae81890e702b9090055ed30e65bea92231
Reviewed-on: https://chromium-review.googlesource.com/1094816
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Marc-Antoine Ruel <maruel@chromium.org>
Commit-Queue: Marc-Antoine Ruel <maruel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565984}
2 files changed