code: function addonsManager_setCategory(aSpec) {
      var spec = aSpec || { };
      var category = spec.category;
      var waitFor = (spec.waitFor == undefined) ? true : spec.waitFor;
  
      if (!category)
        throw new Error(arguments.callee.name + ": Category not specified.");
  
      this._controller.click(category);
  
      if (waitFor)
        this.waitForCategory({category: category});
    }
docs: Select the given category
  
  @param {object} aSpec
  Information for selecting a category
  Elements: category - Category element
  waitFor  - Wait until the category has been selected
  [optional - default: true]