Use checkout_angle_internal for non-public files The previous flag was too broad, pulling all Chromium internal files. We only need one repository. Bug: angleproject:3630 Bug: chromium:1032708 Change-Id: I8aac322e2f748570432be27f2981f927bd264fce Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1969735 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Cody Northrop <cnorthrop@google.com>