Previously, --send-mail required -r to pass. Now it uses the R=|TBR= lines from
the description, which is much more useful.

R=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/8735018

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@112221 0039d316-1c4b-4281-b951-d872f2087c98