libaudioclient: Add accessors for AudioTrack to TrackPlayerBase

This allows us to change the type of mAudioTrack later without breaking
the build.

Test: trackplayerbase_tests
Change-Id: If4d5731adb0e6ad3d7f10d9f73bb1a0d3e33662b
diff --git a/media/libaudioclient/include/media/TrackPlayerBase.h b/media/libaudioclient/include/media/TrackPlayerBase.h
index fe88116..c7c0fa1 100644
--- a/media/libaudioclient/include/media/TrackPlayerBase.h
+++ b/media/libaudioclient/include/media/TrackPlayerBase.h
@@ -37,7 +37,11 @@
             const media::VolumeShaperConfiguration& configuration,
             const media::VolumeShaperOperation& operation);
 
-    //FIXME move to protected field, so far made public to minimize changes to AudioTrack logic
+    sp<AudioTrack> getAudioTrack() { return mAudioTrack; }
+
+    void clearAudioTrack() { mAudioTrack.clear(); }
+
+    // FIXME: make private once all users switch to getAudioTrack()
     sp<AudioTrack> mAudioTrack;
 
             void setPlayerVolume(float vl, float vr);
diff --git a/media/libaudioclient/tests/trackplayerbase_tests.cpp b/media/libaudioclient/tests/trackplayerbase_tests.cpp
index 7317bf0..a4dba9b 100644
--- a/media/libaudioclient/tests/trackplayerbase_tests.cpp
+++ b/media/libaudioclient/tests/trackplayerbase_tests.cpp
@@ -54,7 +54,7 @@
         mPlayer = new TrackPlayer();
         mPlayer->init(track.get(), mPlayer, PLAYER_TYPE_AAUDIO, AUDIO_USAGE_MEDIA,
                       AUDIO_SESSION_NONE);
-        sp<AudioTrack> playerTrack = mPlayer->mAudioTrack;
+        sp<AudioTrack> playerTrack = mPlayer->getAudioTrack();
         ASSERT_EQ(playerTrack->initCheck(), NO_ERROR);
 
         mBufferSize = mFrameCount * playerTrack->frameSize();
@@ -74,7 +74,7 @@
 
     void playBuffer() {
         bool blocking = true;
-        ssize_t nbytes = mPlayer->mAudioTrack->write(mBuffer.data(), mBufferSize, blocking);
+        ssize_t nbytes = mPlayer->getAudioTrack()->write(mBuffer.data(), mBufferSize, blocking);
         EXPECT_EQ(nbytes, mBufferSize) << "Did not write all data in blocking mode";
     }