background.html

<!DOCTYPE html> 
<html>
<embed type="application/x-vnd-haptics" id="pluginobj" 
       width="0" height="0" />
<script>

// Settings.
settings = {
  get version() {
    return localStorage['version'];
  },
  set version(val) {
    localStorage['version'] = val;
  },
  get debug() {
    var key = localStorage['debug'];
    return (typeof key == 'undefined') ? false : key === 'true';
  },
  set debug(val) {
    localStorage['debug'] = val;
    plugin.debug = val;
  },
  get opt_out() {
    var key = localStorage['opt_out'];
    return (typeof key == 'undefined') ? true : key === 'true';
  },
  set opt_out(val) {
    localStorage['opt_out'] = val;
  },
};

// Plugin.
plugin = document.getElementById('pluginobj');

/**
 * Get the version number from the manifest.
 *
 * @returns {string} The current version number.
 */
function getVersion() {
  var version = 'NaN';
  var xhr = new XMLHttpRequest();
  xhr.open('GET', chrome.extension.getURL('manifest.json'), false);
  xhr.send(null);
  var manifest = JSON.parse(xhr.responseText);
  return manifest.version;
}

/**
 * Open a singleton page, which means, if a page already exists, it
 * just selects it.
 *
 * @param url The page which it will navigate to.
 */
function openSingletonPage(url) {
  chrome.windows.getCurrent(function(win) {
    chrome.tabs.getAllInWindow(win.id, function(tabs) {
      for (var i = 0; i < tabs.length; i++) {
        if (tabs[i].url.indexOf(url) == 0) {
          chrome.tabs.update(tabs[i].id, {selected: true});
          return;
        }
      }
      chrome.tabs.create({url: url});
    });
  });
}

/**
 * Hook for installation.
 */
function onInstall() {
}

/**
 * Hook for updates.
 */
function onUpdate() {
  // Do not send updates if the user is opt'd out!
  if (!settings.opt_out) {
    // chrome.tabs.create({url: 'updates.html'});
  }
}

/**
 * Initialization routine.
 */
function init() {
  // Check if the version has changed. In case we want to do something in the
  // future.
  var currVersion = getVersion();
  var prevVersion = settings.version
  if (currVersion != prevVersion) {
    // Update the version incase we want to do something in future.
    settings.version = currVersion;
    
    // Check if we just installed this extension.
    if (typeof prevVersion == 'undefined') {
      onInstall();
    } else {
      onUpdate();
    }
  }
  
  // Sets the debugger according to the settings. 
  plugin.debug = settings.debug;
}


init();</script>
</html>