Make the buffering spinner visible against the black background.
Make the buffering spinner visible against the black background.

Fixes #2110.

Change-Id: I76ea189af91ece6bbc7f15ac3e0b8885aa4e3bb1

tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player