Update HTMLCollection.namedItem() to use the id/name cache

Update HTMLCollection.namedItem() to use the id/name cache. HTMLCollection
maintains an id/name cache internally. It was used by namedItems() method but
strangely not by the namedItem() one.

This change is good for performance as HTMLCollection.namedItem() will now use
the cache when available and thus avoid traversing the DOM tree unnecessarily.

There should be not web-exposed behavior change. This functionality is covered
by a decent amount of layout tests.

The CL also gets rid of HTMLCollection::checkForNameMatch() method as it is no
longer used. HTMLCollection::updateNameCache() already has the same checks
inlined.

R=arv, adamk

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166498

[arv (Not doing code reviews), 2014-02-04 21:00:29]

LGTM

[Inactive, 2014-02-05 00:04:26]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-02-05 00:04:32]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/154183002/1

[commit-bot: I haz the power, 2014-02-05 00:41:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/154183002/1

[commit-bot: I haz the power, 2014-02-05 01:11:23]

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

[commit-bot: I haz the power, 2014-02-05 01:11:24]

Retried try job too often on win_blink_rel for step(s) blink_heap_unittests,
blink_platform_unittests, webkit_lint, webkit_python_tests, webkit_tests,
webkit_unit_tests, wtf_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[Inactive, 2014-02-05 01:18:17]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-02-05 01:18:37]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/154183002/1

[commit-bot: I haz the power, 2014-02-05 03:45:20]

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

[commit-bot: I haz the power, 2014-02-05 03:45:21]

Retried try job too often on win_blink_rel for step(s) blink_heap_unittests,
blink_platform_unittests, webkit_lint, webkit_python_tests, webkit_tests,
webkit_unit_tests, wtf_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_blink_...

[Inactive, 2014-02-05 13:23:38]

The CQ bit was checked by ch.dumez@samsung.com

[commit-bot: I haz the power, 2014-02-05 13:23:50]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/154183002/1

[commit-bot: I haz the power, 2014-02-05 14:18:42]

Change committed as 166498