Instantiate SingleStateQueue<AudioTimestamp>

as typedef AudioTimestampSingleStateQueue and use it in MonoPipe.

Change-Id: Idaebb362bd9d0a81a7ed83792ab9369dc37c0e74
diff --git a/media/libnbaio/MonoPipe.cpp b/media/libnbaio/MonoPipe.cpp
index a74b49e..b55be83 100644
--- a/media/libnbaio/MonoPipe.cpp
+++ b/media/libnbaio/MonoPipe.cpp
@@ -42,7 +42,10 @@
         // mWriteTs
         mSetpoint((reqFrames * 11) / 16),
         mWriteCanBlock(writeCanBlock),
-        mIsShutdown(false)
+        mIsShutdown(false),
+        // mTimestampShared
+        mTimestampMutator(&mTimestampShared),
+        mTimestampObserver(&mTimestampShared)
 {
     CCHelper tmpHelper;
     status_t res;