fix(toolbar): use old toolbar logic for showing screenshare

I don't understand the old showDesktopSharingButton action
but I've tried my best to copy it over. There is an existing
issue where the keyboard shortcut gets registered when it
probably shouldn't because screensharing is disabled. It will
be fixed soon with refactoring of the entire logic determining
whether or not to show the screensharing button.

lang/main.json

         "documentClose": "Close shared document",
         "sharedvideo": "Share a YouTube video",
         "sharescreen": "Screen share",
-        "sharescreenDisabled": "Screen share disabled",
         "stopSharedVideo": "Stop YouTube video",
         "fullscreen": "View / Exit full screen",
         "sip": "Call SIP number",

react/features/toolbox/components/ToolboxV2.web.js

      */
     _conference: Object,
 
+    /**
+     * Whether or not desktopsharing was explicitly configured to be disabled.
+     */
+    _desktopSharingDisabledByConfig: boolean,
+
     /**
      * Whether or not screensharing is initialized.
      */
      * @returns {void}
      */
     _onToolbarToggleScreenshare() {
+        if (!this.props._desktopSharingEnabled) {
+            return;
+        }
+
         sendAnalytics(createShortcutEvent(
             'toggle.screen.sharing',
             ACTION_SHORTCUT_TRIGGERED,
     }
 
     /**
-     * Renders a button for togglein screen sharing.
+     * Renders a button for toggleing screen sharing.
      *
      * @private
-     * @returns {ReactElement}
+     * @returns {ReactElement|null}
      */
     _renderDesktopSharingButton() {
-        const { _desktopSharingEnabled, _screensharing, t } = this.props;
+        const {
+            _desktopSharingDisabledByConfig,
+            _desktopSharingEnabled,
+            _screensharing,
+            t
+        } = this.props;
+
+        const disabledTooltipText
+            = interfaceConfig.DESKTOP_SHARING_BUTTON_DISABLED_TOOLTIP;
+        const showDisabledTooltip
+            = disabledTooltipText && _desktopSharingDisabledByConfig;
+        const visible = _desktopSharingEnabled || showDisabledTooltip;
+
+        if (!visible) {
+            return null;
+        }
+
         const classNames = `icon-share-desktop ${
             _screensharing ? 'toggled' : ''} ${
             _desktopSharingEnabled ? '' : 'disabled'}`;
-        const tooltip = _desktopSharingEnabled
-            ? t('toolbar.sharescreen')
-            : interfaceConfig.DESKTOP_SHARING_BUTTON_DISABLED_TOOLTIP
-                || t('toolbar.sharescreenDisabled');
+        const tooltip = showDisabledTooltip
+            ? disabledTooltipText
+            : t('toolbar.sharescreen');
 
         return (
             <ToolbarButtonV2
     } = state['features/base/conference'];
     const {
         callStatsID,
+        disableDesktopSharing,
         enableRecording,
         enableUserRolesBasedOnToken,
         iAmRecorder
         _chatOpen: current === 'chat_container',
         _conference: conference,
         _desktopSharingEnabled: desktopSharingEnabled,
+        _desktopSharingDisabledByConfig: disableDesktopSharing,
         _dialOutAvailable: isDialOutAvailable,
         _dialog: Boolean(state['features/base/dialog'].component),
         _editingDocument: Boolean(state['features/etherpad'].editing),