Make perf test runner more robust.

Make perf test runner more robust.

Convert all results to floats and log errors on failing
conversions. Otherwise these results bubble up into
buildbot.

TBR=tandrii@chromium.org
BUG=chromium:374740
LOG=n
NOTRY=true

Committed: https://crrev.com/af1eb2258c9a59c14d2904975326ef5e58e12b67
Cr-Commit-Position: refs/heads/master@{#25913}

[Michael Achenbach, 2014-12-21 10:23:42]

machenbach@chromium.org changed reviewers:
+ bmeurer@chromium.org, tandrii@chromium.org

[Michael Achenbach, 2014-12-21 10:24:38]

PTAL

[Michael Achenbach, 2014-12-21 10:24:41]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2014-12-21 10:25:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/811483008/1

[commit-bot: I haz the power, 2014-12-21 10:25:25]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-21 10:25:40]

Patchset 1 (id:??) landed as
https://crrev.com/af1eb2258c9a59c14d2904975326ef5e58e12b67
Cr-Commit-Position: refs/heads/master@{#25913}

[tandrii_google, 2014-12-22 13:08:39]

tandrii@google.com changed reviewers:
+ tandrii@google.com

[tandrii_google, 2014-12-22 13:08:39]

lgtm