There was a bug in voiceover mode. When reading messages, Voiceover
would read out "message author: message content" for each chat bubble,
but the message author was always the name of the chat. So if it was
a contact chat, every message would be read as if from the other party,
and if it was a group chat, every message would be from the title of
the group.
This patch looks up the display name for the given signal id so
Voiceover reads the correct name for each message. It will read "Me" if
the message is outgoing.
b40f6acd01
