Don't match empty style rules.

Don't match empty style rules.

If a style rule has no declarations, skip selector matching unless we are
matching for the inspector which expects empty rules to be included.

The render tree dump for the first-letter-first-line-hover.html test did
include a [color=#008000] for the first-letter renderer with this change.
Most likely because this change avoids a hover recalc since not trying to
match p:hover causes the hover flag not to be set on P. And that the
render tree is different after doing a recalc on the first-letter, for
some reason.

Instead of rebasing the result, I made it a ref-test.

R=esprehn@chromium.org
BUG=448610
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=188731

[rune, 2015-01-16 13:43:14]

PTAL

[esprehn, 2015-01-16 18:52:27]

It seems like this uncovered a bug in first letter? Why would anything change
styles after this...

[rune, 2015-01-19 14:07:21]

On 2015/01/16 18:52:27, esprehn wrote:
> It seems like this uncovered a bug in first letter? Why would anything change
> styles after this...

The first-letter bug is
https://code.google.com/p/chromium/issues/detail?id=450002 which is visible
through getComputedStyle if ::first-letter is recalculated on hover.

With this CL, nothing is recalculated on hover and the green color is correct in
the computed style, and the dumped render tree.

[rune, 2015-01-21 07:53:44]

@esprehn: I've reported the issue and landed a test-case for the bug that
materialized in the expected result here before my changes. Could we proceed
with this CL disregarding that bug?

[esprehn, 2015-01-21 08:55:58]

lgtm

[rune, 2015-01-21 09:11:07]

The CQ bit was checked by rune@opera.com

[commit-bot: I haz the power, 2015-01-21 09:11:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/829393005/1

[commit-bot: I haz the power, 2015-01-21 10:25:04]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=188731