Allow active sheets to have nullptr for RuleSet.

Allow active sheets to have nullptr for RuleSet.

CSSStyleSheets which have a non-matching media attribute may have a
nullptr for RuleSet since it's not needed. Handle that in active style-
sheet diffing. That means adding a sheet with non-matching media should
not cause any style recalculations.

R=meade@chromium.org
BUG=567021
Committed: https://crrev.com/bb06955a67e20f613553b44a7b89c2ae0a2ba5f1
Cr-Commit-Position: refs/heads/master@{#423804}

[rune, 2016-10-06 12:46:01]

The CQ bit was checked by rune@opera.com to run a CQ dry run

[commit-bot: I haz the power, 2016-10-06 12:46:22]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[rune, 2016-10-06 13:12:54]

ptal

[commit-bot: I haz the power, 2016-10-06 14:27:23]

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

[commit-bot: I haz the power, 2016-10-06 14:27:24]

Dry run: This issue passed the CQ dry run.

[meade_UTC10, 2016-10-07 00:58:22]

lgtm

[rune, 2016-10-07 05:59:10]

The CQ bit was checked by rune@opera.com

[commit-bot: I haz the power, 2016-10-07 05:59:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-07 06:05:07]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-10-07 06:06:46]

Description was changed from

==========
Allow active sheets to have nullptr for RuleSet.

CSSStyleSheets which have a non-matching media attribute may have a
nullptr for RuleSet since it's not needed. Handle that in active style-
sheet diffing. That means adding a sheet with non-matching media should
not cause any style recalculations.

R=meade@chromium.org
BUG=567021
==========

to

==========
Allow active sheets to have nullptr for RuleSet.

CSSStyleSheets which have a non-matching media attribute may have a
nullptr for RuleSet since it's not needed. Handle that in active style-
sheet diffing. That means adding a sheet with non-matching media should
not cause any style recalculations.

R=meade@chromium.org
BUG=567021

Committed: https://crrev.com/bb06955a67e20f613553b44a7b89c2ae0a2ba5f1
Cr-Commit-Position: refs/heads/master@{#423804}
==========

[commit-bot: I haz the power, 2016-10-07 06:06:47]

Patchset 1 (id:??) landed as
https://crrev.com/bb06955a67e20f613553b44a7b89c2ae0a2ba5f1
Cr-Commit-Position: refs/heads/master@{#423804}