startFraction method
Assumes that duration
is the total length of the video that this
DurationRange is a segment form. It returns the percentage that start is
through the entire video.
For example, assume that the entire video is 4 minutes long. If start has
a duration of one minute, this will return 0.25
since the DurationRange
starts 25% of the way through the video's total length.
Implementation
double startFraction(Duration duration) {
return start.inMilliseconds / duration.inMilliseconds;
}