Add contentDescription for ListRow, HeaderItem and fast lane

This allows app to

1. customize the contentDescription in BrowseFragment fast lane by
calling HeaderItem.setContentDescription(),  by default HeaderItem
.getName() is used.

2. customize the contentDesciption of each ListRow so talkback
will announce "in $contentDescription list" when moving between rows.

3. Announce when entering "navigation menu" of BrowseFragment

Change-Id: I3006a91c4e8e9bcd72ed0114394ba93b7f3c0295
7 files changed