Pass license check script for most of the tree.

Modified license-checker script to allow pruning directories
we know to be ok.

Still need to do a bit of third_party/* , as well as
file a bunch of bugs on pieces where the licenses aren't clear,
but I'm running out of energy.

Review URL: http://codereview.chromium.org/1100003

Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: e64b3d8f98945fd2ea47b68fb677265ca2633cba