[#928933] Ensure duration value is consistent
[#939997] Do not fire progress event in youtube if loaded data is 0.
[#940715] Media ready callbacks were called in the incorrect order.
[#940444] Ensure youtube wrapper can handle multiple source changes
Bug 898607 - Listen for durationchange events so internal data tracking events can be adjusted
Merge remote-tracking branch 'upstream/master' into footnote-display-option