Document ownership area for rbyers, vollick and rune in core/OWNERS

Add a few comments to core/OWNERS

We've now agreed to document areas of ownership in core/OWNERS
(https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/StkI3k4Pm5U/i5PdztzMgNMJ).
This adds a few descriptions of areas people gave me on a blink-core-owners-discuss thread
back in May.

NOTRY=True
BUG=None

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=185379

[Rick Byers, 2014-11-14 16:51:54]

rbyers@chromium.org changed reviewers:
+ vollick@chromium.org

[Rick Byers, 2014-11-14 16:51:55]

Ian, PTAL

[Ian Vollick, 2014-11-14 16:54:23]

On 2014/11/14 16:51:55, Rick Byers wrote:
> Ian, PTAL

my bit lgtm with a nit: s/tntegration/integration/

[Rick Byers, 2014-11-14 17:09:41]

On 2014/11/14 16:54:23, vollick wrote:
> On 2014/11/14 16:51:55, Rick Byers wrote:
> > Ian, PTAL
> 
> my bit lgtm with a nit: s/tntegration/integration/

Thanks, fixed.

This is sufficiently trivial that I'm not going to block on review from everyone
(I already promised I'd just submit this for people to save them the effort). 
Rune, feel free to TBR me on any change you want to your comment.

[Rick Byers, 2014-11-14 17:10:27]

The CQ bit was checked by rbyers@chromium.org

[commit-bot: I haz the power, 2014-11-14 17:11:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/723063005/20001

[commit-bot: I haz the power, 2014-11-14 17:11:57]

Committed patchset #2 (id:20001) as 185379

[rune, 2014-11-14 21:33:46]

On 2014/11/14 at 17:09:41, rbyers wrote:

> This is sufficiently trivial that I'm not going to block on review from
everyone (I already promised I'd just submit this for people to save them the
effort).  Rune, feel free to TBR me on any change you want to your comment.

lgtm