Add support for GPU acceleration in headless Chromium for Linux

Bug: 617551, 765284
Test: headless_shell --use-gl=egl

Change-Id: Id35866d675bac896aa73cca48e479b5b1efdee38
Reviewed-on: https://chromium-review.googlesource.com/c/1474442
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Joone Hur <joone.hur@intel.com>
Cr-Commit-Position: refs/heads/master@{#637081}
2 files changed