Add instructions on how to run glmark2+ANGLE on Linux Bug: angleproject:3125 Change-Id: I70d295d7ec1dbafc74add068165c5fbcadb48560 Reviewed-on: https://chromium-review.googlesource.com/c/1450222 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>