function MdChipCtrl ($scope, $element, $mdConstant, $timeout, $mdUtil) {
  /**
   * @type {$scope}
   */
  this.$scope = $scope;

  /**
   * @type {$element}
   */
  this.$element = $element;

  /**
   * @type {$mdConstant}
   */
  this.$mdConstant = $mdConstant;

  /**
   * @type {$timeout}
   */
  this.$timeout = $timeout;

  /**
   * @type {$mdUtil}
   */
  this.$mdUtil = $mdUtil;

  /**
   * @type {boolean}
   */
  this.isEditing = false;

  /**
   * @type {MdChipsCtrl}
   */
  this.parentController = undefined;

  /**
   * @type {boolean}
   */
  this.enableChipEdit = false;
}
Controller for the MdChip component. Responsible for handling keyboard
events and editing the chip if needed.

@param $scope
@param $element
@param $mdConstant
@param $timeout
@param $mdUtil
@constructor