UCommonVideoPlayer/Electra does not work in 5.3

This appears to be connected to playing immediately upon opening.
This behavior is not observed when in the Release-5.1 or Release-5.2 streams. With the same setup, the video will start playing on the widget as soon as it is opened.
This appears to be related to playing the media source before it has finished opening.

1. Download the attached test project “VideoPlayerTest”
2. Open the level “TestMap”
3. Play in Editor
4. Watch the instance of “BP_VideoWidget” in the level (the actor has a widget component displaying an instance of “WBP_VideoPlayerWidget”).
5. Observe that the video on the widget is opened, but does not play (the C++ base class of “WBP_VideoPlayerWidget”, “UCommonVideoPlayerWidget”, sets the media source for the video player then plays it during construction of the widget).