Hide some components rather than unmounting (#2271)

Hide some components rather than unmounting them to allow to show again
quickly and keep the view state such as the scrolled offset.

app/assets/javascripts/components/features/ui/containers/status_list_container.jsx

@@ -40,6 +40,8 @@ const makeMapStateToProps = () => {
   const getStatusIds = makeGetStatusIds();
 
   const mapStateToProps = (state, props) => ({
+    scrollKey: props.scrollKey,
+    shouldUpdateScroll: props.shouldUpdateScroll,
     statusIds: getStatusIds(state, props),
     isLoading: state.getIn(['timelines', props.type, 'isLoading'], true),
     isUnread: state.getIn(['timelines', props.type, 'unread']) > 0,

app/assets/javascripts/components/features/ui/index.jsx

@@ -127,9 +127,9 @@ class UI extends React.PureComponent {
       mountedColumns = (
         <ColumnsArea>
           <Compose withHeader={true} />
-          <HomeTimeline trackScroll={false} />
-          <Notifications trackScroll={false} />
-          {children}
+          <HomeTimeline shouldUpdateScroll={() => false} />
+          <Notifications shouldUpdateScroll={() => false} />
+          <div style={{display: 'flex', flex: '1 1 auto', position: 'relative'}}>{children}</div>
         </ColumnsArea>
       );
     }