Skip Display::prepareForCall calls everywhere except Mac. Display::prepareForCall was added for CGL and EAGL backends which need to know when an EGL call on a new thread is about to happen. Making this virtual call on all EGL calls on all platforms adds overhead which we can avoid so compile out prepareForCall everywhere except Mac. Bug: angleproject:8434 Change-Id: I7b50463ed405a73eb993e18eb4f83434b4a4fd6e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5582015 Commit-Queue: Geoff Lang <geofflang@chromium.org> Auto-Submit: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>