Revert "Do not acknowledge flush() on start() for static tracks"

This reverts commit cafe86a9cb6625bb1ec6383e16e28e4c9e455f87.

Bug: 23924093.
Change-Id: I186d1013b06a286eca93c30bb9b3545dc36695ff
diff --git a/services/audioflinger/Tracks.cpp b/services/audioflinger/Tracks.cpp
index d058255..f7da209 100644
--- a/services/audioflinger/Tracks.cpp
+++ b/services/audioflinger/Tracks.cpp
@@ -712,12 +712,9 @@
             // But in this case we know the mixer thread (whether normal mixer or fast mixer)
             // isn't looking at this track yet:  we still hold the normal mixer thread lock,
             // and for fast tracks the track is not yet in the fast mixer thread's active set.
-            // TODO: remove race condition on stop() followed by start().
-            if (mSharedBuffer == 0) {  // only streaming tracks use flush().
-                ServerProxy::Buffer buffer;
-                buffer.mFrameCount = 1;
-                (void) mAudioTrackServerProxy->obtainBuffer(&buffer, true /*ackFlush*/);
-            }
+            ServerProxy::Buffer buffer;
+            buffer.mFrameCount = 1;
+            (void) mAudioTrackServerProxy->obtainBuffer(&buffer, true /*ackFlush*/);
         }
     } else {
         status = BAD_VALUE;