Add --force as a synonym for --no_presubmit as per Nicolas' request.

Factor out some code in FilterFlag() to make the code much more readable.

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/119315

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@17884 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed