5054b2a99c
The test runner sends a "show" command to the test clients and assumes this was enough work done by the client to enable the compositor to map the window. Now that we wait to show a Wayland window until the first buffer is attached (see bug 750552), we need to make sure that we attach a buffer before assuming that we have the final stacking order. So, to in order to continue relying on "show" to be enough to actually show a window, let the test client wait until it has drawn the first frame. This makes the tests using Wayland clients test non-flaky. https://bugzilla.gnome.org/show_bug.cgi?id=754711