[CSS Grid Layout] Avoid unneeded calls to hasDefiniteLogicalSize()

[CSS Grid Layout] Avoid unneeded calls to hasDefiniteLogicalSize()

r189895 was introducing a performance regression on grid layout tests.
The problem is that hasDefiniteLogicalSize() is slower than the previous
check (logicalSize.isIntrinsicOrAuto()).

However, it's not needed to call always hasDefiniteLogicalSize(), only
when the values are percentages. Thus, this patch is modifying the logic
to only call hasDefiniteLogicalSize() when it's really needed in order
to reduce the performance overhead.

BUG=457606
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191145

[Manuel Rego, 2015-02-23 11:18:54]

rego@igalia.com changed reviewers:
+ eae@chromium.org, jchaffraix@chromium.org, leviw@chromium.org

[eae, 2015-02-23 20:01:03]

Makes sense to me but I'd like either Julien or Levi to take a look as well,
they know this code better than I do.

[Julien - ping for review, 2015-03-02 21:26:34]

The CQ bit was checked by jchaffraix@chromium.org

[Julien - ping for review, 2015-03-02 21:26:35]

lgtm

[commit-bot: I haz the power, 2015-03-02 21:28:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/948833002/20001

[commit-bot: I haz the power, 2015-03-02 23:09:49]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191145