wayland: Don't skip notifying about initial maximized size

When a client wants to start initialized it my set the maximized state
before having attached any buffers. Before we'd not notify the client of
the new expected size if the previous size was 0x0 as it would normally
mean we'd resize to 1x1, but since this is not always the case, only
avoid notifying the client if the previous size was 0x0 and the result
is 1x1.

https://bugzilla.gnome.org/show_bug.cgi?id=745303

src/wayland/window-wayland.c

@@ -205,15 +205,21 @@ meta_window_wayland_move_resize_internal (MetaWindow                *window,
           constrained_rect.height != window->rect.height ||
           (flags & META_MOVE_RESIZE_STATE_CHANGED))
         {
-          /* If we get a 0x0 size, this means that we're trying to resize
-           * a surface that doesn't have any buffer attached. This can happen
-           * when a client requests an xdg surface before bringing it up.
-           * The constrained_rect will be 1x1 because of how our constraints
-           * code works, and sending that to the window would cause it to
-           * redraw itself, so just don't send anything.
-           */
+          /* If the constrained size is 1x1 and the unconstrained size is 0x0
+           * it means that we are trying to resize a window where the client has
+           * not yet committed a buffer. The 1x1 constrained size is a result of
+           * how the constraints code works. Lets avoid trying to have the
+           * client configure itself to draw on a 1x1 surface.
+           *
+           * We cannot guard against only an empty unconstrained_rect here,
+           * because the client may have created a xdg surface without a buffer
+           * attached and asked it to be maximized. In such case we should let
+           * it know about the expected window geometry of a maximized window,
+           * even though there is currently no buffer attached. */
           if (unconstrained_rect.width == 0 &&
-              unconstrained_rect.height == 0)
+              unconstrained_rect.height == 0 &&
+              constrained_rect.width == 1 &&
+              constrained_rect.height == 1)
             return;
 
           meta_wayland_surface_configure_notify (window->surface,