Merge "Update AudioFlinger to use templated unique_lock" into main

    // the Thread is not busy releasing the Tracks, during which the Thread mutex

    // may be temporarily unlocked.  Some Track methods will use this method to

    // avoid races.

    virtual void waitWhileThreadBusy_l(audio_utils::unique_lock& ul)

    virtual void waitWhileThreadBusy_l(audio_utils::unique_lock<audio_utils::mutex>& ul)

            REQUIRES(mutex()) = 0;

    // The ThreadloopExecutor is used to defer functors or dtors

     * ThreadBase_Mutex during this time.  No other mutex is held.

     */

    void waitWhileThreadBusy_l(audio_utils::unique_lock& ul) final REQUIRES(mutex()) {

    void waitWhileThreadBusy_l(audio_utils::unique_lock<audio_utils::mutex>& ul)

            final REQUIRES(mutex()) {

        // the wait returns immediately if the predicate is satisfied.

        mThreadBusyCv.wait(ul, [&]{ return mThreadBusy == false;});

    }