Add new API AudioRecord::notificationFrames()

     */

            uint32_t    getSampleRate() const   { return mSampleRate; }

    /* Return the notification frame count.

     * This is approximately how often the callback is invoked, for transfer type TRANSFER_CALLBACK.

     */

            size_t      notificationFrames() const  { return mNotificationFramesAct; }

    /* Sets marker position. When record reaches the number of frames specified,

     * a callback with event type EVENT_MARKER is called. Calling setMarkerPosition

     * with marker == 0 cancels marker notification callback.