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https://dvcs.w3.org/hg/dap/raw-file/default/media-stream-capture/ImageCapture.html#widl-ImageCapture-takePhoto-void "if the readyState of the VideoStreamTrack provided in the constructor is not "live", the UA must fire a ImageCaptureErrorEvent event at the ImageCapture object with a new ImageCaptureError object whose code is set to INVALID_TRACK" INVALID_TRACK is not defined in ImageCaptureError interface.