EAGL: Remove the impl preprocessor guards Adhere to the project formatting: - Remove #if preprocessor guards from the EAGL implementation. - Order the includes as in style guide - Use include / import consistently - Move GLES_SILENCE_DEPRECIATION into .gn, similar to CGL - Remove or add platform.h include based on whether the file itself actually the platform.h defined macros Simplifies the nested preprocessor macros. Makes it simpler to further fix the preprocessor use. WebKit should instead have a non-ANGLE .mm file #importing the implementations with the proper include guards. Bug: angleproject:8121 Change-Id: I775bedd048fe3382f873abffb693f130f6104c5c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4404158 Auto-Submit: Kimmo Kinnunen <kkinnunen@apple.com> Commit-Queue: Kenneth Russell <kbr@chromium.org> Reviewed-by: Dan Glastonbury <djg@apple.com> Reviewed-by: Kenneth Russell <kbr@chromium.org>