Deleting words that are before current playback time, does not update current playback time

[ghost]

If the user deletes a section of text that occurs before the current playback time then the current playback time on the clock (and hence, the scrubber) should updated. This doesn't happen.

To clarify, this bug occurs in the video preview controller clock and not the scrubber component.

Expected Behaviour
The current playback time should be reduced if a section of video from earlier in the video playback, is deleted.

To reproduce

1. Press play
2. Select a couple of words (or just 1, a couple makes the bug easier to see)
3. Wait for the video playback to progress past the words you have selected
4. Delete those words
5. Observe that the current playback time clock does not get updated