Include all the preparatory work to eventually update the R= line to match the
actual reviewers.

The goal here is that ChangeDescription becomes the official implementation for
handling and modifying commit messages accross git-cl, gcl and the commit queue.

This change does slightly tweak the spacing between the hot lines.
It is done on purpose to make them consistent.

R=dpranke@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/13741015

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@193514 0039d316-1c4b-4281-b951-d872f2087c98