FullScreen Immersive on KitKat and above devices still shows device buttons

Enable fullscreen immersive on kitkat and above devices does not properly work on devices with onscreen buttons.

1. Create a new template project
2. Go to Edit > Project Settings > select "Enable FullScreen Immersive on KitKat and above devices".
3. Launch project to an onscreen button device such as LG G2 or Nexus 5

Expected: The buttons should hide when fullscreen immersive is on.
Result: Onscreen buttons show up on the splash screen and in game.