fixed #2459: Because the interval attribute of DeviceMotionEvent is read-only and different in every browser, The setAccelerometerInterval function is invalid. So we fixed this bug by calculating interval values.
fixed #2459: because the interval attribute of DeviceMotionEvent is read only and different on every browser. the setAccelerometerInterval function is invalid.  so we fixed this bug by calculating interval values.
Merge pull request #1539 from ShengxiangChen/issue2459_accelerometerBug

fixed #2459: because the interval attribute of DeviceMotionEvent is read only and different on every browser. the setAccelerometerInterval function is invalid.  so we fixed this bug by calculating interval values.