Fix performance issue with EXT_multisampled_render_to_texture Adding a dirty flag to the mMSTexInfo struct so that the multisampled texture does not get unnecessarily resolved on each call. Bug: chromium:1019199 Change-Id: Ia9b24cd0a7f2d82f83f20f7e60f9f2b23383ec6f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1910531 Reviewed-by: Rafael Cintron <rafael.cintron@microsoft.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>