Merge "update AlwaysOnHotwordDetector javadoc"

     * Callbacks for always-on hotword detection.

     */

    public static abstract class Callback {

        /**

         * Called when the hotword availability changes.

         * This indicates a change in the availability of recognition for the given keyphrase.

         * It's called at least once with the initial availability.<p/>

         * Updates the availability state of the active keyphrase and locale on every keyphrase

         * sound model change.

         *

         * <p>This API is called whenever there's a possibility that the keyphrase associated

         * with this detector has been updated. It is not guaranteed that there is in fact any

         * change, as it may be called for other reasons.</p>

         *

         * <p>This API is also guaranteed to be called right after an AlwaysOnHotwordDetector

         * instance is created to updated the current availability state.</p>

         *

         * Availability implies whether the hardware on this system is capable of listening for

         * the given keyphrase or not. <p/>

         * <p>Availability implies the current enrollment state of the given keyphrase. If the

         * hardware on this system is not capable of listening for the given keyphrase,

         * {@link AlwaysOnHotwordDetector#STATE_HARDWARE_UNAVAILABLE} will be returned.

         *

         * @see AlwaysOnHotwordDetector#STATE_HARDWARE_UNAVAILABLE

         * @see AlwaysOnHotwordDetector#STATE_KEYPHRASE_UNSUPPORTED

         * @see AlwaysOnHotwordDetector#STATE_KEYPHRASE_UNENROLLED

         * @see AlwaysOnHotwordDetector#STATE_KEYPHRASE_ENROLLED

         */