Only call glInvalidateFramebuffer if it is available. BUG=angleproject:885 Change-Id: I30a9bcebc80805aea0c12d9c67194b7b0c98200f Reviewed-on: https://chromium-review.googlesource.com/263475 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org> Tested-by: Geoff Lang <geofflang@chromium.org>