Wake Lock API demo

External references:

• https://developer.mozilla.org/en-US/docs/Web/API/Navigator/requestWakeLock
• http://www.w3.org/TR/wake-lock/
• http://stackoverflow.com/questions/33933555/prevent-android-chrome-from-going-idle-auto-locking-sleeping-phone
• https://github.com/richtr/NoSleep.js
• ...
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