Update DeviceMotionEvent IDL to match the specification.

third_party/WebKit/Source/modules/device_orientation/DeviceMotionEvent.h

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 40 matching lines @@
     return new DeviceMotionEvent(eventType, deviceMotionData);
   }
 
   DeviceMotionData* getDeviceMotionData() const {
     return m_deviceMotionData.get();
   }
 
   DeviceAcceleration* acceleration();
   DeviceAcceleration* accelerationIncludingGravity();
   DeviceRotationRate* rotationRate();
-  double interval(bool& isNull) const;
+  double interval() const;
 
   const AtomicString& interfaceName() const override;
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   DeviceMotionEvent();
   DeviceMotionEvent(const AtomicString&, const DeviceMotionEventInit&);
   DeviceMotionEvent(const AtomicString& eventType, DeviceMotionData*);
 
   Member<DeviceMotionData> m_deviceMotionData;
   Member<DeviceAcceleration> m_acceleration;
   Member<DeviceAcceleration> m_accelerationIncludingGravity;
   Member<DeviceRotationRate> m_rotationRate;
 };
 
 DEFINE_TYPE_CASTS(DeviceMotionEvent,
                   Event,
                   event,
                   event->interfaceName() == EventNames::DeviceMotionEvent,
                   event.interfaceName() == EventNames::DeviceMotionEvent);
 
 }  // namespace blink
 
 #endif  // DeviceMotionEvent_h