Fix SimpleSignatureTest to use getDeclaredClasses when checking API.

It was originally using getClasses(), which would only return public
classes, not protected ones. However, protected inner classes are part
of the API such as AsynchonousQueryHandler.WrapperArgs.

(cherry picked from commit 75ad38a48bbdd201515c2b5c3fa91c854718ede0)

Change-Id: I455af62346210af29d9ca796c13509527c7fce38
1 file changed