[ios] fix sublayer resize It's only macOS that supports autoresizing mask on CALayers. In case of iOS, a sublayer has to be resized manually. Fixes FramebufferTest_ES3.SurfaceDimensionsChangeAnd\ FragCoord/ES3_Metal test. Bug: angleproject:7994 Change-Id: Ie4f08480a581e7b1b8cfb7e9b47ec3afadc0484f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4403974 Commit-Queue: Maksim Sisov <msisov@igalia.com> Reviewed-by: Kenneth Russell <kbr@chromium.org>