Adjust source paths so we don't need to use rebase_path() on all of them.

BUG=angleproject:1569

Change-Id: I1af7678dd8961405446fec49731eba5294bcb586
Reviewed-on: https://chromium-review.googlesource.com/1196046
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>