fix(screenshare): remove redundant event / only show on supported env (#9100)

* remove redundant event / only show on supported env

* remove unused imports

react/features/base/conference/middleware.web.js

 // @flow
 
-import UIEvents from '../../../../service/UI/UIEvents';
 import { setPrejoinPageVisibility, setSkipPrejoinOnReload } from '../../prejoin';
 import { JitsiConferenceErrors } from '../lib-jitsi-meet';
 import { MiddlewareRegistry } from '../redux';
-import { TOGGLE_SCREENSHARING } from '../tracks/actionTypes';
 
 import { CONFERENCE_FAILED, CONFERENCE_JOINED } from './actionTypes';
 import './middleware.any';
 
         break;
     }
-    case TOGGLE_SCREENSHARING: {
-        if (typeof APP === 'object') {
-            APP.UI.emitEvent(UIEvents.TOGGLE_SCREENSHARING, action.audioOnly);
-        }
-
-        break;
-    }
     }
 
     return next(action);

react/features/base/environment/environment.js

     return Platform.OS === 'macos';
 }
 
+/**
+ * Returns whether or not the current OS is Windows.
+ *
+ * @returns {boolean}
+ */
+export function isWindows() {
+    return Platform.OS === 'windows';
+}
+
 /**
  * Returns whether or not the current browser or the list of passed in browsers
  * is considered suboptimal. Suboptimal means it is a supported browser but has

react/features/screen-share/functions.js

 // @flow
 
-import { isMacOS } from '../base/environment';
+import { isWindows } from '../base/environment';
 import { browser } from '../base/lib-jitsi-meet';
 
 
 }
 
 /**
- * Returns the visibility of the audio only screen share button. Currently electron on mac os doesn't
- * have support for this functionality.
+ * Returns the visibility of the audio only screen share button. Currently only chrome browser and electron on
+ * windows supports this functionality.
  *
  * @returns {boolean}
  */
 export function isScreenAudioSupported() {
-    return !(browser.isElectron() && isMacOS());
+    return browser.isChrome() || (browser.isElectron() && isWindows());
 }