@Override
    public void onResize() {
        if (!isResizing) {
            // Attempt immediate layout so the display appears to update immediately.
            doLayout();
            // Now do deferred layout to compensate for delayed attachment of children.
            doDelayedLayout();
        } else {
            super.onResize();
        }
    }
The element that masks the screen so we can catch mouse events over
iframes.
stroom-core-client-widget/src/main/java/com/google/gwt/user/client/ui/MySplitLayoutPanel.java