Allow track buffer "allocation" to be from pipe

Change-Id: Ib9ac170f8e8b7746b3588157a56cbee3b753a1cb
diff --git a/services/audioflinger/Threads.h b/services/audioflinger/Threads.h
index cc2b246..4683a13 100644
--- a/services/audioflinger/Threads.h
+++ b/services/audioflinger/Threads.h
@@ -301,6 +301,8 @@
                 // If a thread does not have such a heap, this method returns 0.
                 virtual sp<MemoryDealer>    readOnlyHeap() const { return 0; }
 
+                virtual sp<IMemory> pipeMemory() const { return 0; }
+
     mutable     Mutex                   mLock;
 
 protected: