This reverts commit 51603c63.

Reason for revert: Fixed issue that broke Skia build

Original change's description:
> Revert "Use is_apple instead of is_mac and is_ios everywhere"
>
> This reverts commit 2762641a.
>
> Reason for revert: is_apple is not universally defined. Breaks ANGLE roll into Skia.
>
> Original change's description:
> > Use is_apple instead of is_mac and is_ios everywhere
> >
> > Bug: chromium:1161513
> > Change-Id: Id7d582f127f4b79ea6fc5b8ad39fff768c45f477
> > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2611312
> > Reviewed-by: James Darpinian <jdarpinian@chromium.org>
> > Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
> > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
>
> TBR=jdarpinian@chromium.org,syoussefi@chromium.org
>
> Bug: chromium:1161513
> Change-Id: I831e60149f410044a79d9f66aa9ddd9902410fd7
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2618039
> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>

TBR=jdarpinian@chromium.org,syoussefi@chromium.org

Bug: chromium:1161513
Change-Id: I3cf30aa047a1f208fa7d1acda1d6d4e5da7b6ad5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2622244Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>