Abstract the use of textures in EGL. BUG=18110152 Change-Id: I02e85817532de599109a9e3938badc5e48bb29c0 Reviewed-on: https://swiftshader-review.googlesource.com/1261 Reviewed-by: Nicolas Capens <nicolascapens@google.com> Tested-by: Nicolas Capens <nicolascapens@google.com>