.search() may return results in unexpected order. Manually sort the entries
otherwise first_day and last_day could be inversed, leading to negative number
of days.

R=iannucci@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/16003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@203792 0039d316-1c4b-4281-b951-d872f2087c98