Add serializers to RTCIceCandidate and RTCSessionDescription

Add serializers to RTCIceCandidate and RTCSessionDescription

Support for the serializer syntax was added by these CLs:
  https://codereview.chromium.org/1031593003/
  https://codereview.chromium.org/1004503004/

The V8ObjectBuilder helper class was added by this CL:
  https://codereview.chromium.org/1031783003/

BUG=469650, 468180
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192621

[Jens Widell, 2015-03-26 09:32:11]

jl@opera.com changed reviewers:
+ perkj@chromium.org, tommi@chromium.org

[Jens Widell, 2015-03-26 09:32:11]

PTAL

[tommi (sloooow) - chröme, 2015-03-26 09:51:59]

lgtm! awesome :D

[perkj_chrome, 2015-03-26 10:32:34]

lgtm- thanks a lot!

[Jens Widell, 2015-03-26 12:18:44]

The CQ bit was checked by jl@opera.com

[commit-bot: I haz the power, 2015-03-26 12:18:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1033983002/1

[commit-bot: I haz the power, 2015-03-26 14:35:42]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-03-26 14:35:43]

Try jobs failed on following builders:
  linux_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/5...)

[Jens Widell, 2015-03-26 15:38:33]

On 2015/03/26 14:35:43, I haz the power (commit-bot) wrote:
> Try jobs failed on following builders:
>   linux_blink_rel on tryserver.blink (JOB_FAILED,
>
http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/5...)

The new toJSON() method showed up in the
webexposed/global-interface-listing.html test's output, as expected. Test
expectations adjusted.

[Jens Widell, 2015-03-26 15:38:38]

The CQ bit was checked by jl@opera.com

[Jens Widell, 2015-03-26 15:38:39]

The patchset sent to the CQ was uploaded after l-g-t-m from perkj@chromium.org,
tommi@chromium.org
Link to the patchset: https://codereview.chromium.org/1033983002/#ps20001
(title: "fix global-interface-listing expectation")

[commit-bot: I haz the power, 2015-03-26 15:38:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1033983002/20001

[commit-bot: I haz the power, 2015-03-26 18:33:45]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=192621

[Peter Kasting, 2015-03-27 02:40:26]

This might have caused a test failure (not sure); see http://crbug.com/471132 .