audioflinger: forward flush to direct output streams

Track flush should be forwarded to the audio HAL when playing
on a direct output stream.

Bug: 17704953.
Change-Id: Iafc94327fe9aebf1d4eaa97b76c6767b7ac5babe
diff --git a/services/audioflinger/Tracks.cpp b/services/audioflinger/Tracks.cpp
index c0a75b9..75190f3 100644
--- a/services/audioflinger/Tracks.cpp
+++ b/services/audioflinger/Tracks.cpp
@@ -824,6 +824,10 @@
             // remove from active track list, reset(), and trigger presentation complete
             if (playbackThread->mActiveTracks.indexOf(this) < 0) {
                 reset();
+                if (thread->type() == ThreadBase::DIRECT) {
+                    DirectOutputThread *t = (DirectOutputThread *)playbackThread;
+                    t->flushHw_l();
+                }
             }
         }
         // Prevent flush being lost if the track is flushed and then resumed