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/Threads.h b/services/audioflinger/Threads.h
index fd025b5..7af5264 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -894,6 +894,7 @@
 
     virtual     bool        checkForNewParameter_l(const String8& keyValuePair,
                                                    status_t& status);
+    virtual     void        flushHw_l();
 
 protected:
     virtual     int         getTrackName_l(audio_channel_mask_t channelMask,
@@ -929,6 +930,7 @@
     OffloadThread(const sp<AudioFlinger>& audioFlinger, AudioStreamOut* output,
                         audio_io_handle_t id, uint32_t device);
     virtual                 ~OffloadThread() {};
+    virtual     void        flushHw_l();
 
 protected:
     // threadLoop snippets
@@ -941,9 +943,6 @@
     virtual     void        onAddNewTrack_l();
 
 private:
-                void        flushHw_l();
-
-private:
     bool        mHwPaused;
     bool        mFlushPending;
     size_t      mPausedWriteLength;     // length in bytes of write interrupted by pause