Make SelectorChecker::tagMatches internal to the SelectorChecker

Make SelectorChecker::tagMatches internal to the SelectorChecker

SelectorQuery doesn't really want this function since it handles namespaces
and querySelector explicitly doesn't deal with namespaces. Instead we can
use a simpler check in SelectorQuery and move this function into
SelectorChecker.cpp

R=rune@opera.com

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=194702

[esprehn, 2015-04-29 22:58:33]

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

[commit-bot: I haz the power, 2015-04-29 22:58:50]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1108993006/1

[esprehn, 2015-04-30 00:19:50]

esprehn@chromium.org changed reviewers:
+ rune@opera.com, timloh@chromium.org

[commit-bot: I haz the power, 2015-04-30 01:25:50]

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

[commit-bot: I haz the power, 2015-04-30 01:25:51]

Dry run: This issue passed the CQ dry run.

[Timothy Loh, 2015-04-30 05:43:01]

lgtm

[esprehn, 2015-04-30 05:52:47]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2015-04-30 05:53:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1108993006/1

[commit-bot: I haz the power, 2015-04-30 05:53:44]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=194702