Michel Dänzer authored Aug 02, 2016 and Adam Jackson committed Aug 15, 2016

This change has two effects:

1. Only calls FlushCallbacks when we're actually flushing data to a
   client. The unnecessary FlushCallback calls could cause significant
   performance degradation with compositing, which is significantly
   reduced even without any driver changes.

2. By passing the ClientPtr to FlushCallbacks, drivers can completely
   eliminate unnecessary flushing of GPU commands by keeping track of
   whether we're flushing any XDamageNotify events to the client for
   which the corresponding rendering commands haven't been flushed to
   the GPU yet.

Reviewed-by: Adam Jackson <ajax@redha.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>