Refactor Texture::storage methods to use gl::Error objects. BUG=angle:520 Change-Id: I33bc8479815a587749bddc722ac9fe5a85f554cb Reviewed-on: https://chromium-review.googlesource.com/216648 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>