[RN] Toggle audio-only icon based on state

react/features/toolbox/components/Toolbox.native.js

          */
         _audioMuted: React.PropTypes.bool,
 
+        /**
+         * Flag showing whether the audio-only mode is in use.
+         */
+        _audioOnly: React.PropTypes.bool,
+
         /**
          * Flag showing whether room is locked.
          */
                     style = { style }
                     underlayColor = { underlayColor } />
                 <ToolbarButton
-                    iconName = 'visibility'
+                    iconName = {
+                        this.props._audioOnly ? 'visibility-off' : 'visibility'
+                    }
                     iconStyle = { iconStyle }
                     onClick = { this.props._onToggleAudioOnly }
                     style = { style }
  *
  * @param {Object} state - Redux store.
  * @returns {{
+ *     _audioOnly: boolean,
  *     _locked: boolean
  * }}
  * @private
     return {
         ...abstractMapStateToProps(state),
 
+        /**
+         * The indicator which determines whether the conference is in
+         * audio-only mode.
+         *
+         * @protected
+         * @type {boolean}
+         */
+        _audioOnly: Boolean(conference.audioOnly),
+
         /**
          * The indicator which determines whether the conference is
          * locked/password-protected.