fix expand/collapse arrows for youtube videos (#7240)

webapp/components/post_view/post_attachment_opengraph/post_attachment_opengraph.jsx

@@ -107,7 +107,7 @@ export default class PostAttachmentOpenGraph extends React.PureComponent {
     }
 
     componentDidUpdate() {
-        postListScrollChange();
+        setTimeout(postListScrollChange, 0);
     }
 
     fetchData(url) {

webapp/components/post_view/post_body_additional_content.jsx

@@ -134,6 +134,7 @@ export default class PostBodyAdditionalContent extends React.PureComponent {
                     channelId={this.props.post.channel_id}
                     link={link}
                     show={this.state.embedVisible}
+                    onLinkLoaded={this.handleLinkLoaded}
                 />
             );
         }

webapp/components/youtube_video/youtube_video.jsx

@@ -14,7 +14,8 @@ export default class YoutubeVideo extends React.PureComponent {
         channelId: PropTypes.string.isRequired,
         currentChannelId: PropTypes.string.isRequired,
         link: PropTypes.string.isRequired,
-        show: PropTypes.bool.isRequired
+        show: PropTypes.bool.isRequired,
+        onLinkLoaded: PropTypes.func
     }
 
     constructor(props) {
@@ -103,6 +104,7 @@ export default class YoutubeVideo extends React.PureComponent {
         } else {
             this.loadWithoutKey();
         }
+        this.props.onLinkLoaded();
     }
 
     loadWithoutKey() {