GitLab

|event_task_runner_| may be nullptr when the browser is passed both
--single-process and --disable-gpu, so a null check is needed.

R=msisov

Change-Id: Ic045be1a70dfa98f269f47df7b9ccbb553a181d7
Bug: 1042170
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2004073
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Maksim Sisov <msisov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#732473}