shift-click the video button to screenshare rather than overriding the button entirely.

src/CallHandler.js

@@ -158,6 +158,12 @@ function _onAction(payload) {
             newCall.placeVoiceCall();
         }
         else if (payload.type === 'video') {
+            newCall.placeVideoCall(
+                payload.remote_element,
+                payload.local_element
+            );
+        }
+        else if (payload.type === 'screensharing') {
             newCall.placeScreenSharingCall(
                 payload.remote_element,
                 payload.local_element

src/controllers/molecules/RoomHeader.js

@@ -69,10 +69,10 @@ module.exports = {
         });
     },
 
-    onVideoClick: function() {
+    onVideoClick: function(e) {
         dis.dispatch({
             action: 'place_call',
-            type: "video",
+            type: e.shiftKey ? "screensharing" : "video",
             room_id: this.props.room.roomId
         });
     },