This starts at 5 seconds (used to be 15) and goes up to ~60 seconds on the tenth round.

BUG=None
TEST=None
Review URL: http://codereview.chromium.org/3326004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@58488 0039d316-1c4b-4281-b951-d872f2087c98