Refactor using concrete EGL object pointers. Bug 20045861 Change-Id: I3dc737b5cc5759e487245030bfd8d871eacd8124 Reviewed-on: https://swiftshader-review.googlesource.com/2793 Tested-by: Nicolas Capens <capn@google.com> Reviewed-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Nicolas Capens <capn@google.com>