Use benchmark_name (date-time) instead of revision number for telemetry html

Use benchmark_name (date-time) instead of revision number for telemetry html
results.

Chromium src revision number doesn't work when telemetry is moved to catapult
and is not that useful anyway.

After this patch, results.html will look like this: http://i.imgur.com/FdNXkkH.png

BUG=497905
Committed: https://crrev.com/27e4e3e9c965a73dfe735d1620a26ff1cf5ace2f
Cr-Commit-Position: refs/heads/master@{#334609}

[nednguyen, 2015-06-12 19:09:48]

nednguyen@google.com changed reviewers:
+ aiolos@chromium.org, dtu@chromium.org

[nednguyen, 2015-06-16 00:42:23]

nednguyen@google.com changed reviewers:
+ sullivan@chromium.org

[sullivan, 2015-06-16 05:09:15]

lgtm

[nednguyen, 2015-06-16 14:46:59]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2015-06-16 14:47:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1178843003/1

[commit-bot: I haz the power, 2015-06-16 15:44:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-16 15:45:31]

Patchset 1 (id:??) landed as
https://crrev.com/27e4e3e9c965a73dfe735d1620a26ff1cf5ace2f
Cr-Commit-Position: refs/heads/master@{#334609}