wlt: toolkit: fix forcing redraw during unneeded resize-round

wlt: toolkit: fix forcing redraw during unneeded resize-round

If we resize the buffers, we skip redrawing as resizing implies this.
However, if the resize-handler skips resizing because the size didn't
change, it also skips redrawing.
Hence, we add a new flag to force redrawing even if the resize-operation
is skipped. This fixes a bug where we didn't redraw during stalling resize
operations by the user.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>