feat(toolbox): introduce ToolboxItem

This abstraction represents an action which can go anywhere in a toolbox (be
that the main toolbar or the overflow menu) and it's platform independent.

It does not depend on Redux, thus making it stateless, which facilitates its use
in stateful button implementations as well as stateless ones.

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

@@ -127,30 +127,23 @@ class Toolbox extends Component<Props> {
      * button to get styles for.
      * @protected
      * @returns {{
-     *     iconName: string,
      *     iconStyle: Object,
      *     style: Object
      * }}
      */
     _getMuteButtonStyles(mediaType) {
-        let iconName;
         let iconStyle;
         let style;
 
         if (this.props[`_${mediaType}Muted`]) {
-            iconName = `${mediaType}MutedIcon`;
             iconStyle = styles.whitePrimaryToolbarButtonIcon;
             style = styles.whitePrimaryToolbarButton;
         } else {
-            iconName = `${mediaType}Icon`;
             iconStyle = styles.primaryToolbarButtonIcon;
             style = styles.primaryToolbarButton;
         }
 
         return {
-
-            // $FlowExpectedError
-            iconName: this[iconName],
             iconStyle,
             style
         };
@@ -174,9 +167,9 @@ class Toolbox extends Component<Props> {
                 key = 'primaryToolbar'
                 pointerEvents = 'box-none'
                 style = { styles.primaryToolbar }>
-                <AudioMuteButton buttonStyles = { audioButtonStyles } />
+                <AudioMuteButton styles = { audioButtonStyles } />
                 <HangupButton />
-                <VideoMuteButton buttonStyles = { videoButtonStyles } />
+                <VideoMuteButton styles = { videoButtonStyles } />
             </View>
         );
 
@@ -263,20 +256,6 @@ class Toolbox extends Component<Props> {
     }
 }
 
-/**
- * Additional properties for various icons, which are now platform-dependent.
- * This is done to have common logic of generating styles for web and native.
- * TODO As soon as we have common font sets for web and native, this will no
- * longer be required.
- */
-// $FlowExpectedError
-Object.assign(Toolbox.prototype, {
-    audioIcon: 'microphone',
-    audioMutedIcon: 'mic-disabled',
-    videoIcon: 'camera',
-    videoMutedIcon: 'camera-disabled'
-});
-
 /**
  * Maps redux actions to {@link Toolbox}'s React {@code Component} props.
  *