Update camera continuous autofocus javadoc.

    // than FOCUS_MODE_CONTINUOUS_VIDEO. Auto focus starts when the parameter is

    // set.

    //

    // If applications call CameraHardwareInterface.autoFocus in this mode, the

    // focus callback will immediately return with a boolean that indicates

    // whether the focus is sharp or not. The apps can then decide if they want

    // to take a picture immediately or to change the focus mode to auto, and

    // run a full autofocus cycle. The focus position is locked after autoFocus

    // call. If applications want to resume the continuous focus,

    // cancelAutoFocus must be called. Restarting the preview will not resume

    // the continuous autofocus. To stop continuous focus, applications should

    // change the focus mode to other modes.

    // Applications can call CameraHardwareInterface.autoFocus in this mode. If

    // the autofocus is in the middle of scanning, the focus callback will

    // return when it completes. If the autofocus is not scanning, focus

    // callback will immediately return with a boolean that indicates whether

    // the focus is sharp or not. The apps can then decide if they want to take

    // a picture immediately or to change the focus mode to auto, and run a full

    // autofocus cycle. The focus position is locked after autoFocus call. If

    // applications want to resume the continuous focus, cancelAutoFocus must be

    // called. Restarting the preview will not resume the continuous autofocus.

    // To stop continuous focus, applications should change the focus mode to

    // other modes.

    static const char FOCUS_MODE_CONTINUOUS_PICTURE[];

private: