[CSS Grid Layout] Add GridSpan::iterator

[CSS Grid Layout] Add GridSpan::iterator

As suggested when GridResolvedPosition was introduced, this patch
adds a GridSpan::iterator which allows to simplify the loops over
GridResolvedPositions.

BUG=258258
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=172404

[Manuel Rego, 2014-04-11 22:53:16]

This was suggested at https://codereview.chromium.org/166623002/#msg6

[Julien - ping for review, 2014-04-21 19:00:07]

https://codereview.chromium.org/235663004/diff/1/Source/core/rendering/style/...
File Source/core/rendering/style/GridCoordinate.h (right):

https://codereview.chromium.org/235663004/diff/1/Source/core/rendering/style/...
Source/core/rendering/style/GridCoordinate.h:180: }
It would be better to match the WTF iterator API, which matches the STL.

IMO this API matches too much what the old code does (by doing it <= itlast()
instead of it != it.end()) and to an extend assumes a linear iteration without
any gap.

[Manuel Rego, 2014-04-22 22:40:15]

On 2014/04/21 19:00:07, Julien Chaffraix - PST wrote:
>
https://codereview.chromium.org/235663004/diff/1/Source/core/rendering/style/...
> File Source/core/rendering/style/GridCoordinate.h (right):
> 
>
https://codereview.chromium.org/235663004/diff/1/Source/core/rendering/style/...
> Source/core/rendering/style/GridCoordinate.h:180: }
> It would be better to match the WTF iterator API, which matches the STL.
> 
> IMO this API matches too much what the old code does (by doing it <= itlast()
> instead of it != it.end()) and to an extend assumes a linear iteration without
> any gap.

Yes, I agree. I've just uploaded a new patch following this idea.

[Julien - ping for review, 2014-04-23 15:30:31]

Not a huge fan of the next() calls but I could live with it. LGTM

[Manuel Rego, 2014-04-23 17:31:26]

The CQ bit was checked by rego@igalia.com

[commit-bot: I haz the power, 2014-04-23 17:31:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rego@igalia.com/235663004/20001

[commit-bot: I haz the power, 2014-04-23 21:17:26]

Change committed as 172404