AudioContext, HTMLMediaElement, and MediaStream provide currentTime to content scripts
The worst offender is probably AudioContext, where you can get the current time thus:
var audioContext = new AudioContext();
audioContext.currentTime;Similarly, HTMLVideoElement.currentTime, HTMLAudioElement.currentTime, and CanvasCaptureMediaStream.currentTime can each be used as a time source with resolution better than 10 ms.
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