updateStorage_(opt_callback) {
    var keyName = e2e.ext.util.ChromeStorageLocal.STORAGE_KEY_NAME_;
    chrome.storage.local.get(keyName, goog.bind(function(values) {
      this.storage_ = values[keyName] || {};
      opt_callback && opt_callback(this);
    }, this));
  }
@param {function(!e2e.ext.util.ChromeStorageLocal)=} opt_callback
@private