Upstream support for iOS Simulator. Originally authored in the WebKit repository: https://bugs.webkit.org/show_bug.cgi?id=205618 Has been tested with WebKit's WebGL backend on top of ANGLE inside the iOS Simulator. TODOs will be addressed in forthcoming CLs. Bug: angleproject:4263 Change-Id: Ic879866aaee5f933599d956b0646d0c01db55d0d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1995824 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Commit-Queue: Kenneth Russell <kbr@chromium.org>