Add missing import on gr-rest-api-interface.html in gr-app

Change-Id: Ia13667fc91d272fd8c04af36c9a8c2e976ca4823
diff --git a/polygerrit-ui/app/elements/gr-app.html b/polygerrit-ui/app/elements/gr-app.html
index ef93794..ced27dd 100644
--- a/polygerrit-ui/app/elements/gr-app.html
+++ b/polygerrit-ui/app/elements/gr-app.html
@@ -55,6 +55,7 @@
 <link rel="import" href="./settings/gr-registration-dialog/gr-registration-dialog.html">
 <link rel="import" href="./settings/gr-settings-view/gr-settings-view.html">
 <link rel="import" href="./shared/gr-fixed-panel/gr-fixed-panel.html">
+<link rel="import" href="./shared/gr-rest-api-interface/gr-rest-api-interface.html">
 
 <script src="../scripts/util.js"></script>