FramebufferGL: Add a member to know if we are the default FBO On CGL, the default framebuffer will have a name different than 0 and without this change it wouldn't get special-cased as on the other platforms. It is assumed that the default framebuffer will get initialized directly by the driver or other parts of the code. BUG=angleproject:891 Change-Id: Ifbe4ada58f27ad9ddb5b43697c234cb17e7504f0 Reviewed-on: https://chromium-review.googlesource.com/290147 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>