var webView:StageWebView = new StageWebView();
webView.stage = this.stage;
webView.viewPort = new Rectangle( 0, 0, 200, 200 );
webView.loadURL( "http://www.example.com" );
So here we are setting the viewport rectangle to have it's topleft corner at 0,0 and the bottom right corner at 200,200.
You can then have a regular button on the stage at say 250,250 to remove the stagewebview.
