Remove hasResolver() check from Document::updateStyle.

Remove hasResolver() check from Document::updateStyle.

The resolver cannot disappear in the middle of a style recalc, lets
ASSERT about that and remove the check. I also fixed the crash bug in
tracing that oysteine@ found when tracing could be turned on in the
middle of style recalc and we'd have missed calling setStatsEnabled at
the start of the recalc.

BUG=501634
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197513

[esprehn, 2015-06-19 21:52:16]

esprehn@chromium.org changed reviewers:
+ dstockwell@chromium.org, ojan@chromium.org, oysteine@chromium.org

[esprehn, 2015-06-19 21:52:22]

The CQ bit was checked by esprehn@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-06-19 21:53:03]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1199563003/20001

[commit-bot: I haz the power, 2015-06-19 22:42:02]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-19 22:42:03]

Dry run: Try jobs failed on following builders:
  mac_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/mac_blink_rel/builds/59866)

[ojan, 2015-06-20 00:57:10]

The CQ bit was checked by ojan@chromium.org

[ojan, 2015-06-20 00:57:10]

lgtm

[commit-bot: I haz the power, 2015-06-20 00:57:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1199563003/20001

[commit-bot: I haz the power, 2015-06-20 01:01:26]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197513