Handle relaunch requests from the iframe

Only attach the message listener when the modal is displaying. This prevents multiple listeners being set up by multiple registration components on the page.

Also, scope the `onMessage` handler to that component's iframe, so that we don't respond to other component's messages.

src/components/registration/registration.jsx

@@ -13,13 +13,27 @@ var Registration = React.createClass({
     },
     onMessage: function (e) {
         if (e.origin != window.location.origin) return;
+        if (e.source != this.refs.registrationIframe.contentWindow) return;
         if (e.data == 'registration-done') this.props.onRegistrationDone();
+        if (e.data == 'registration-relaunch') {
+            this.refs.registrationIframe.contentWindow.location.reload();
+        }
+    },
+    toggleMessageListener: function (present) {
+        if (present) {
+            window.addEventListener('message', this.onMessage);
+        } else {
+            window.removeEventListener('message', this.onMessage);
+        }
     },
     componentDidMount: function () {
-        window.addEventListener('message', this.onMessage);
+        if (this.props.isOpen) this.toggleMessageListener(true);
+    },
+    componentDidUpdate: function (prevProps) {
+        this.toggleMessageListener(this.props.isOpen && !prevProps.isOpen);
     },
     componentWillUnmount: function () {
-        window.removeEventListener('message', this.onMessage);
+        this.toggleMessageListener(false);
     },
     render: function () {
         var frameSettings = {
@@ -32,7 +46,7 @@ var Registration = React.createClass({
                     onRequestClose={this.props.onRequestClose}
                     className="registration"
                     frameSettings={frameSettings}>
-                <iframe src="/accounts/standalone-registration/" {...frameSettings} />
+                <iframe ref="registrationIframe" src="/accounts/standalone-registration/" {...frameSettings} />
             </Modal>
         );
     }