Remove references from .gn to third_party/mesa

third_party/mesa is no longer part of Chromium, and having it
listed here enforces gn checks for any product that still
checks out mesa in third_party (i.e. Google Chrome) which is
a problem.

Bug: 873321
Change-Id: If1c28fb2c393f04c9b0fe0703204fd7225a1a483
Commit-Queue: Scott Graham <>
Reviewed-by: Scott Graham <>
Cr-Commit-Position: refs/heads/master@{#607653}
1 file changed