Make the default framebuffer owned by Surface In CGL there is no notion of default Framebuffer and MakeCurrent only makes a context current but not a drawable. Instead, everything is done via render to texture. For that reason, different surfaces will have different FBOs as default framebuffers, which causes that change. BUG=angleproject:891 Change-Id: I3f6da7b587353316026ea39a5c87f91265e0f1ba Reviewed-on: https://chromium-review.googlesource.com/289872 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>