title: Chrome extension popup showing by condition
body: <p>I want to show popup by click, but only if condition is false.
  After click to extension icon background js searchig for tab with current name. If tab found background js continues working. If not found - i want to show popup with instructions. Can`t understand how to just show popup in this case.
  I can set popup by browserAction.setPopup(), but popup will be displayed only after next clicks.
  I just want to show my popup one time.
  It is definitely posible, I've seen this behavior on other extension.</p>
  
  <pre><code>var pcTabs; // tabs array
  
  chrome.browserAction.onClicked.addListener(buttonClick);
  
  function buttonClick() {
   // getting tabs...
   if(pcTabs.length != 0){
      // working with finded tabs
   } else{ // tabs not found
      // show popup.html here. this is the question
   }
  }
  </code></pre>
  
  <p><strong>upd</strong>.
  This is my <a href="https://github.com/illuzor/Play-Button-For-Pocket-Casts/blob/master/source/background.js" rel="noreferrer">background.js</a>. All code also in repository.
  How to replace alerts to popups?</p>