Use sp<AudioTrack> instead of raw AudioTrack *

This change prepares for the new implementation of AudioTrack client, which
will require clients to use only sp<AudioTrack>, not raw AudioTrack *.
A raw delete will cause a race condition during AudioTrack destruction.

AudioTrack was made a RefBase by commit b68a91a70bc8d0d18e7404e14443d4e4020b3635
on 2011/11/15, when it was needed by OpenSL ES (for the callback protector).
At that time, the only other client that was also converted from
AudioTrack * to sp<AudioTrack> was android.media.AudioTrack JNI in
project frameworks/base (file android_media_AudioTrack.cpp).

Details:
 * Use .clear() instead of delete followed by = NULL.
 * ALOG %p need .get().
 * sp<> don't need to be listed in constructor initializer, if initially 0.
 * Use == 0 for sp<> vs == NULL for raw pointers.
 * Use if (sp != 0) instead of if (raw).

Change-Id: Ic7cad25795d6e862e112abdc227b6d33afdfce17
diff --git a/media/libmedia/JetPlayer.cpp b/media/libmedia/JetPlayer.cpp
index 59e538f..8fe5bb3 100644
--- a/media/libmedia/JetPlayer.cpp
+++ b/media/libmedia/JetPlayer.cpp
@@ -39,7 +39,6 @@
         mMaxTracks(maxTracks),
         mEasData(NULL),
         mEasJetFileLoc(NULL),
-        mAudioTrack(NULL),
         mTrackBufferSize(trackBufferSize)
 {
     ALOGV("JetPlayer constructor");
@@ -140,11 +139,10 @@
         free(mEasJetFileLoc);
         mEasJetFileLoc = NULL;
     }
-    if (mAudioTrack) {
+    if (mAudioTrack != 0) {
         mAudioTrack->stop();
         mAudioTrack->flush();
-        delete mAudioTrack;
-        mAudioTrack = NULL;
+        mAudioTrack.clear();
     }
     if (mAudioBuffer) {
         delete mAudioBuffer;