Make MessageAttachmentTile focusable so it handles key
events.

The attachment_tile_push_state exists to draw the blue
background when the attachment is focused or clicked, but
isn't the click handler. It needs to duplicate the MAT's
state to retain this behavior once we switch the focusable
thing from it to the MAT.

Bug: 7564727
Change-Id: I5293fa1bb1a662cdf5263b39c67328df68c0fdd9
1 file changed