The DeviceOrientationEvent and DeviceMotionEvent constructors are defined by the DeviceOrientation Event Specification but were not were not implemented in Chrome. Firefox has already shipped these constructors as specified.
Docs: https://developer.mozilla.org/en-US/docs/Web/API/DeviceOrientationEvent https://developer.mozilla.org/en-US/docs/Web/API/DeviceMotionEvent
Samples: http://w3c-test.org/orientation-event/idlharness.html