Allow TRANSFER_OBTAIN to be used for fast tracks

Change-Id: I8fa20c26f076567b38210af4a680fe1cb2eacee4
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index 3474f24..ef889aa 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -1545,9 +1545,10 @@
               (
                 (sharedBuffer != 0)
               ) ||
-              // use case 2: callback handler and frame count is default or at least as large as HAL
+              // use case 2: frame count is default or at least as large as HAL
               (
-                (tid != -1) &&
+                // we formerly checked for a callback handler (non-0 tid),
+                // but that is no longer required for TRANSFER_OBTAIN mode
                 ((frameCount == 0) ||
                 (frameCount >= mFrameCount))
               )