Domain Reliablity: Add "domain" field to reports.

Domain Reliablity: Add "domain" field to reports.

Add a "domain" field that returns the hostname of the original request.
This lets sites with wildcard contexts tell which subdomain triggered the
beacons they receive.

BUG=

Committed: https://crrev.com/1e1d803bda102882f6afebab7d6bce04d262c8d7
Cr-Commit-Position: refs/heads/master@{#296947}

[Deprecated (see juliatuttle), 2014-09-24 19:43:13]

ttuttle@chromium.org changed reviewers:
+ davidben@chromium.org

[Deprecated (see juliatuttle), 2014-09-24 19:43:13]

PTAL, davidben. FYI, pavlos.

[davidben, 2014-09-26 15:28:02]

lgtm

[Deprecated (see juliatuttle), 2014-09-26 15:32:27]

The CQ bit was checked by ttuttle@chromium.org

[commit-bot: I haz the power, 2014-09-26 15:33:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/605473002/1

[commit-bot: I haz the power, 2014-09-26 15:37:24]

Committed patchset #1 (id:1) as ffee7790e380753b8c08bf3cf69e1d79f1fcb52a

[commit-bot: I haz the power, 2014-09-26 15:38:06]

Patchset 1 (id:??) landed as
https://crrev.com/1e1d803bda102882f6afebab7d6bce04d262c8d7
Cr-Commit-Position: refs/heads/master@{#296947}