Get rid of the overloads on templated traversal methods for clarity and safety

Get rid of the overloads on templated traversal methods for clarity and safety

After careful thought, these overloads decrease clarity and safety for marginal
benefit.  Because we have the dichotomy between Node and ContainerNode we do not
want to call the hidden method Node::firstChild when we pass a ContainerNode to
the traversal method and thus incur the cost of the extra check.  It is best to
be explicit to decrease the likelyhood that someone will inadvertantly use the
slower hidden method when traversing.

BUG=331880
R=ch.dumez@samsung.com, esprehn@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=164795

[atreat, 2014-01-08 18:37:13]

The one linux bot failure is the gclient revert issue(s) that have been popping
up.  Please review?

[Inactive, 2014-01-08 19:15:29]

lgtm for core/

[eseidel, 2014-01-09 00:42:14]

There was a perf regression filed this morning from these traversal changes. 
I'd like to see that triaged at least before we continue down this path?

[Inactive, 2014-01-09 00:49:33]

On 2014/01/09 00:42:14, eseidel wrote:
> There was a perf regression filed this morning from these traversal changes. 
> I'd like to see that triaged at least before we continue down this path?

Adam, could you check if this patch fixes the perf regression?

[atreat, 2014-01-09 15:00:31]

On 2014/01/09 00:49:33, Chris Dumez wrote:
> On 2014/01/09 00:42:14, eseidel wrote:
> > There was a perf regression filed this morning from these traversal changes.

> > I'd like to see that triaged at least before we continue down this path?
> 
> Adam, could you check if this patch fixes the perf regression?

Will do.  First to try and reproduce...

[eseidel, 2014-01-09 16:26:14]

lgtm.

[commit-bot: I haz the power, 2014-01-09 17:07:36]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/adam.treat@samsung.com/128823002/1

[commit-bot: I haz the power, 2014-01-09 18:55:30]

Change committed as 164795