code: function (target, callback) {
              GestureRecognizer.call(this, target, callback);
  
              // Intentionally not documented.
              this._scale = 1;
  
              // Intentionally not documented.
              this._offsetScale = 1;
  
              // Intentionally not documented.
              this.referenceDistance = 0;
  
              // Intentionally not documented.
              this.interpretThreshold = 20;
  
              // Intentionally not documented.
              this.weight = 0.4;
  
              // Intentionally not documented.
              this.pinchTouches = [];
          }
docs: Constructs a pinch gesture recognizer.
  @alias PinchRecognizer
  @constructor
  @augments GestureRecognizer
  @classdesc A concrete gesture recognizer subclass that looks for two finger pinch gestures.
  @param {EventTarget} target The document element this gesture recognizer observes for mouse and touch events.
  @param {Function} callback An optional function to call when this gesture is recognized. If non-null, the
  function is called when this gesture is recognized, and is passed a single argument: this gesture recognizer,
  e.g., <code>gestureCallback(recognizer)</code>.
  @throws {ArgumentError} If the specified target is null or undefined.