Integrity.

packages/filebrowser-extension/package.json

@@ -40,6 +40,7 @@
     "@jupyterlab/services": "^3.2.1-alpha.0",
     "@phosphor/algorithm": "^1.1.2",
     "@phosphor/commands": "^1.6.1",
+    "@phosphor/messaging": "^1.2.2",
     "@phosphor/widgets": "^1.6.0"
   },
   "devDependencies": {