Add a MailNotifier that notifies chrome-security-bugs--@google.com for LKGR builds.

Add a MailNotifier that notifies chrome-security-bugs--@google.com for LKGR builds.

This is a re-implementation of https://codereview.chromium.org/1241393002/.

R=inferno@chromium.org,mbarbella@chromium.org,ochang@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=296189

[ghost stip (do not use), 2015-07-31 20:49:36]

ptal

[ghost stip (do not use), 2015-07-31 20:53:07]

(go ahead and CQ if it looks good, it will take effect immediately and can be
immediately reverted. check
https://build.chromium.org/p/chromium.gatekeeper/builders/Chromium%20Gatekeeper
for any problems)

[aarya, 2015-07-31 21:04:50]

aarya@google.com changed reviewers:
+ aarya@google.com

[aarya, 2015-07-31 21:04:50]

The CQ bit was checked by aarya@google.com

[aarya, 2015-07-31 21:04:50]

lgtm

[commit-bot: I haz the power, 2015-07-31 21:05:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1271613002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1271613002/1

[inferno, 2015-07-31 21:05:23]

lgtm

[commit-bot: I haz the power, 2015-07-31 21:07:14]

Committed patchset #1 (id:1) as
http://src.chromium.org/viewvc/chrome?view=rev&revision=296189

[Oliver Chang, 2015-08-05 18:02:51]

We don't seem to have gotten any emails for a very recent breakage:
http://build.chromium.org/p/chromium.lkgr/builders. 

stip, could you please check that the settings are correct?