Metal: Re-add flush to eglBindTexImage but as NoWait Removing the flush entirely caused performance regressions on a couple of benchmarks because the GPU became idle waiting for work. Re-add the flush but with NoWait so there is no CPU/GPU sychronization. Bug: chromium:1466696, chromium:1467392 Change-Id: I5e2d1ca7b7a4590e3e668d2cd214d09d28c4b085 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4718007 Reviewed-by: Quyen Le <lehoangquyen@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>