// from select and translate chrome extension

chrome.contextMenus.create({title: "Add or Remove languages", contexts:["selection"], onclick: options}); 

function options(info)
{
  var options = null;
  if (!info.linkUrl || info.linkUrl.lenght == 0) {
    options = info.selectionText; ///// <<<<<<------- there's the selection magic
  }
  chrome.tabs.create({url: "options.html" });
}