If loaded first, Python can then be used to replace JS bootstrapping
logic if appropriate libs are already present in depot_tools.

BUG=328453
AUTHOR=techtonik@gmail.com
R=iannucci@chromium.org, maruel@chromium.org

Review URL: https://codereview.chromium.org/140183007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@257248 0039d316-1c4b-4281-b951-d872f2087c98