Import licences.py from Chromium.
Import licences.py from Chromium.

This is an unmodified copy from Chromium rev
a60a62ef75a1f261eb884ceaed5a068e577b84b3

I will fix 'scan' to pass in a follow-up change
and teach sky/tools/deploy.py how to use 'credits'
output to create a CREDITS.sky file in another change.

I expect us to diverge from Chromium's licences.py so
I have not made this sync from Chromium, but we may
want to consider that in the future.

R=abarth@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/968303002

jianglu/mojo,collinjackson/mojo,collinjackson/mojo,chinmaygarde/mojo,collinjackson/mojo,collinjackson/mojo,jianglu/mojo,collinjackson/mojo,jianglu/mojo,afandria/mojo,jianglu/mojo,chinmaygarde/mojo,jianglu/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,collinjackson/mojo,afandria/mojo,jianglu/mojo,afandria/mojo,afandria/mojo,afandria/mojo,collinjackson/mojo,chinmaygarde/mojo,afandria/mojo,afandria/mojo,jianglu/mojo,chinmaygarde/mojo,collinjackson/mojo,chinmaygarde/mojo,chinmaygarde/mojo,chinmaygarde/mojo,afandria/mojo,collinjackson/mojo