Waiting on a fence is problematic if using threaded worker to submit work since code needs to know if the work has been submitted or not before doing the wait. Eliminate the wait by using a serial if available or if no serial check the file descriptor directly. If no serial it's because we are waiting on an imported file descriptor. Could call fence.wait in that case but can also wait on the file descriptor. Test: angle_end2end_tests --gtest_filter=EGLSyncTest.*/ES2_Vulkan Bug: b/170312581 Change-Id: I392a5e73ac8f851d0d5bc53f06063568c0c90d2c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2579042Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>