This patch changes the subtitle sync from using a procentage to a
'slider value' that ranges from -300 to 300. The reasons for this is that
WebOS doesn't jump in 0.1 increments but instead jumps 1.0 increments in
the slider, which results in subtitle sync jumping 0.6s per increment.
Using a value from -300 to 300 makes LG WebOS jump 0.1s instead.
Marcus Nilsson