When titlebar's visible height changed, it means the

    protected void onScrollChanged(int l, int t, int oldl, int oldt) {

        super.onScrollChanged(l, t, oldl, oldt);

        sendOurVisibleRect();

        // update WebKit if visible title bar height changed. The logic is same

        // as getVisibleTitleHeight.

        int titleHeight = getTitleHeight();

        if (Math.max(titleHeight - t, 0) != Math.max(titleHeight - oldt, 0)) {

            sendViewSizeZoom();

        }

    }

    @Override

    public boolean dispatchKeyEvent(KeyEvent event) {