To reproduce, open http://jsfiddle.net/0jjnaghw/
Error is logged to browser dev tools (in Chrome & Firefox, somehow not in Safari).

Happens on v15.0.0-rc.2 and on latest master version.

The assignment of additional event data to the newly created SyntheticEvent triggers a console error:
https://github.com/facebook/react/blob/3a4e1dbb5b2957875cab6af11a5e5934e125a0d8/src/test/ReactTestUtils.js#L502

> "Warning: This synthetic event is reused for performance reasons."

simulateNativeEventOnDOMComponent: function(
      topLevelType,
      comp,
      fakeNativeEvent) {
    ReactTestUtils.simulateNativeEventOnNode(
      topLevelType,
      findDOMNode(comp),
      fakeNativeEvent
    );
  },
  nativeTouchData: function(x, y) {
    return {
      touches: [
        {pageX: x, pageY: y},
      ],
    };
  },
  createRenderer: function() {
    return new ReactShallowRenderer();
  },
  Simulate: null,
  SimulateNative: {},
};
/**
 * @class ReactShallowRenderer
 */
var ReactShallowRenderer = function() {
  this._instance = null;
};
ReactShallowRenderer.prototype.getMountedInstance = function() {