Added internal-alerts app to get builder alerts from private Google
trees.

+ Return redirect URL in json object if the user is not logged in.
+ If the logged in user doesn't have google.com email address, then
  return a 403 otherwise return "internal-alerts" stored in the
  memcache.
+ Post method stores the alerts as "internal-alerts" stored in the
  memcache.

R=ojan@chromium.org
BUG=399496

Review URL: https://codereview.chromium.org/518623002

git-svn-id: svn://svn.chromium.org/blink/trunk@181250 bbb929c8-8fbe-4397-9dbb-9b2b20218538