Re-enable frame dropping for non-auto timestamps

This change adds an entire field to note whether the timestamp was
auto-generated by Surface or supplied by the application.

The value is used when deciding whether or not to drop frames based
on buffer presentation timestamps.  If a desired presentation time
was set explicitly, BufferQueue will use that value to decide if a
frame should be dropped.  If the timestamp was generated by Surface
at the time the buffer was queued, the timestamp is ignored.

Bug 10151804

Change-Id: Ibd571a7578351063b813cbdad2ddbeed70655ba5