Fix SoundPool.play() looping regression in 4.3 DO NOT MERGE

The change I7370d6e59a7ef26dfb284a8b058d5ab2e0a42ccf caused a regression
in SoundPool looping when using SoundPool's streaming implementation.
This reverts a portion of that change.

Bug: https://code.google.com/p/android/issues/detail?id=58113
Bug: 10171337
Change-Id: I8af0dc8683a7c7f225c80f0eb4d39770667b52e5
diff --git a/media/libmedia/AudioTrack.cpp b/media/libmedia/AudioTrack.cpp
index 7eeb4f8..2c84605 100644
--- a/media/libmedia/AudioTrack.cpp
+++ b/media/libmedia/AudioTrack.cpp
@@ -557,7 +557,9 @@
 // must be called with mLock held
 status_t AudioTrack::setLoop_l(uint32_t loopStart, uint32_t loopEnd, int loopCount)
 {
-    if (mSharedBuffer == 0 || mIsTimed) {
+    // SoundPool streaming implementation uses AudioTrack EVENT_MORE_DATA callback mode,
+    // and relies on being able to loop the data provided by the most recent callback.
+    if (/*mSharedBuffer == 0 ||*/ mIsTimed) {
         return INVALID_OPERATION;
     }