Remove some redundant code from accessibility table headers

Remove some redundant code from accessibility table headers

headerObject() and headerObjectsForRow/Column methods look very similar.
They do almost exactly the same thing. It looks like some bits could be shared
among them. There would also be less code to maintain.

BUG=none

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190761

[k.czech, 2015-02-23 23:11:48]

k.czech@samsung.com changed reviewers:
+ dmazzoni@chromium.org

[k.czech, 2015-02-24 12:15:20]

On 2015/02/23 23:11:48, k.czech wrote:

I also wanted to make sure that I did not break any logic regarding adding cells
with colspans.
Seems everything is fine, because primaryCellAt for cells with colspan returns
exactly the same cell, even with malformed colspans.
So checking whether particular cell is already added should be enough.

[dmazzoni, 2015-02-24 16:33:34]

The CQ bit was checked by dmazzoni@chromium.org

[dmazzoni, 2015-02-24 16:33:35]

lgtm

Thanks for the cleanup!

[commit-bot: I haz the power, 2015-02-24 16:34:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/942183003/1

[commit-bot: I haz the power, 2015-02-24 17:31:35]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190761