Updates Error 404 component so that we can set 404 status on SSR rend…

…ers (mui#357)

shared/components/DemoApp/Error404/Error404.js

@@ -1,9 +1,26 @@
-import React from 'react';
+import React, { Component, PropTypes } from 'react';
 
-function Error404() {
-  return (
-    <div>Sorry, that page was not found.</div>
-  );
+class Error404 extends Component {
+  componentWillMount() {
+    const { staticContext } = this.context.router;
+    if (staticContext) {
+      staticContext.missed = true;
+    }
+  }
+
+  render() {
+    return (
+      <div>
+        <div>Sorry, that page was not found.</div>
+      </div>
+    );
+  }
 }
 
+Error404.contextTypes = {
+  router: PropTypes.shape({
+    staticContext: PropTypes.object,
+  }).isRequired,
+};
+
 export default Error404;