Fix AudioTrack shared memory leak

    enum {FS_INVALID, FS_FILLING, FS_FILLED, FS_ACTIVE};

    mutable uint8_t     mFillingUpStatus;

    int8_t              mRetryCount;

    const sp<IMemory>   mSharedBuffer;

    // see comment at AudioFlinger::PlaybackThread::Track::~Track for why this can't be const

    sp<IMemory>         mSharedBuffer;

    bool                mResetDone;

    const audio_stream_type_t mStreamType;

    int                 mName;      // track name on the normal mixer,

AudioFlinger::PlaybackThread::Track::~Track()

{

    ALOGV("PlaybackThread::Track destructor");

    // The destructor would clear mSharedBuffer,

    // but it will not push the decremented reference count,

    // leaving the client's IMemory dangling indefinitely.

    // This prevents that leak.

    if (mSharedBuffer != 0) {

        mSharedBuffer.clear();

        // flush the binder command buffer

        IPCThreadState::self()->flushCommands();

    }

}

void AudioFlinger::PlaybackThread::Track::destroy()