title: popup window in Chrome extension
body: <p>I am writing a Chrome extension, and I want a login window to be popped up when users click on the context menu so that user can input username and password. In Chrome extension, I only found <code>chrome.pageAction.setPopup</code> and <code>chrome.browserAction.setPopup</code> can be used to show popup windows,  but they show popups only when the page action's icon or browser action's icon is clicked, not the context menu. Of course, I can use javascript prompt box to do this, but the problem is the password cannot be masked in the prompt box. So I am wondering if there are some other ways to create a popup window in Chrome extension.</p>
  
  <p>Thanks!</p>