Refactor platform code Use switch constructs instead of if-else to allow reuse of code and simplify addition of other platforms as new cases. Bug: angleproject:6902 Change-Id: Ia941d0d7bc03538bbc8d96ebece60224994a6c66 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3532260 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Antonio Caggiano <antonio.caggiano@collabora.com> Commit-Queue: Antonio Caggiano <antonio.caggiano@collabora.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>