Remove gl::Error. Removes several TODOs. Only egl::Error remains. Also slightly decreases binary size. Bug: angleproject:2491 Change-Id: I3a9d1c22eb0884ca9e37362463fddd0083faf826 Reviewed-on: https://chromium-review.googlesource.com/c/1337462 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>