Merge "SoundPool: Fix StreamManager JavaThread shutdown" into rvc-dev

    JavaThread(JavaThread &&) = delete; // uses "this" ptr, not moveable.

    ~JavaThread() {

        join(); // manually block until the future is ready as std::future

                // destructor doesn't block unless it comes from std::async

                // and it is the last reference to shared state.

    }

    void join() const {

        mFuture.wait();

    }

    static int staticFunction(void *data) {

        JavaThread *jt = static_cast<JavaThread *>(data);

        jt->mF();

        jt->mIsClosed = true;

        jt->mPromise.set_value();

        jt->mIsClosed = true;  // publicly inform that we are closed

                               // after we have accessed all variables.

        return 0;

    }