Fix unsupported button tooltips.
Fix unsupported button tooltips.

The refactoring that allowed asset cards to reload their buttons
also ended up breaking the tooltips on unsupported buttons. This
fixes that bug.

Change-Id: Ib33845553de99c8a134529b003c3bd3d319d99bd

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