Parse and render messages synchronously. (zulip#248)

This simplifies (and maybe speeds up) `MessageContainer`.

src/message/MessageContainer.js

@@ -5,31 +5,13 @@ import MessageFull from './MessageFull';
 import MessageBrief from './MessageBrief';
 
 export default class MessageContainer extends React.PureComponent {
-
-  state = {
-    message: null,
-  };
-
-  constructor(props) {
-    super(props);
-    this.renderMessage();
-  }
-
-  async renderMessage() {
-    const { message, auth } = this.props;
-    this.setState({
-      message: await renderHtml(message, auth),
-    });
-  }
-
   render() {
     const { avatarUrl, timestamp, twentyFourHourTime, fromName, fromEmail, isBrief } = this.props;
-    const { message } = this.state;
     const MessageComponent = isBrief ? MessageBrief : MessageFull;
 
     return (
       <MessageComponent
-        message={message}
+        message={renderHtml(this.props.message, this.props.auth)}
         avatarUrl={avatarUrl}
         fromName={fromName}
         fromEmail={fromEmail}

src/message/renderHtml.js

@@ -148,13 +148,13 @@ const parseDom = (dom, auth, baseStyle, onPress) => {
   });
 };
 
-export const renderHtml = (html: string, auth) =>
-  new Promise((resolve, reject) => {
-    const handler = new htmlparser.DomHandler((err, dom) => {
-      if (err) reject(err);
-      resolve(parseDom(dom, auth, [styles.base]));
-    });
-    const parser = new htmlparser.Parser(handler);
-    parser.write(html.replace(/\n|\r/g, ''));
-    parser.done();
+export const renderHtml = (html: string, auth) => {
+  let result = null;
+  const handler = new htmlparser.DomHandler((err, dom) => {
+    if (!err) result = parseDom(dom, auth, [styles.base]);
   });
+  const parser = new htmlparser.Parser(handler);
+  parser.write(html.replace(/\n|\r/g, ''));
+  parser.done();
+  return result;
+};