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/account_timeline/index.jsx

@@ -62,6 +62,7 @@ class AccountTimeline extends React.PureComponent {
 
         <StatusList
           prepend={<HeaderContainer accountId={this.props.params.accountId} />}
+          scrollKey='account_timeline'
           statusIds={statusIds}
           isLoading={isLoading}
           hasMore={hasMore}