GitLab

Tryjobs on this bot try to run the angle_deqp_gles3_tests but it
isn't found causing gn gen to fail. This fixes this issue by adding
the correct gn flag to make ANGLE generate the dEQP targets.

BUG=583702

Review URL: https://codereview.chromium.org/1809803003

Cr-Commit-Position: refs/heads/master@{#381580}