Do not provide a way to use an AsyncTask from a non main thread.

Fix for http://b/issue?id=2539948

This public API can be called from any thread, so do not use an
AsyncTask.  In a separate changelist, the caller now uses an
AsyncTask instead.

Change-Id: I646950964323f8c749f9aa2176226561c6f2b21f
1 file changed