Throttle the refresh of the message list as it changes (fixes #2126515)

* Catch onContentChanged and throttle calls to cursor.requery()
* Use 2.5s for now.  This seems to provide excellent responsiveness
  with little apparent latency.
* Also fixes #2135882

Change-Id: I9cab6558c9cfeb1dbdb5fb250f4f04059db324f7
1 file changed