Migrate typedefs in {event_listeners,extension,formatter,heap_snapshot_worker,help}-legacy.js

Bug: 1006759
Change-Id: Ic2e3b5d8ece70a14cf067c79a14e3695382fa75b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2100910
Commit-Queue: Tim van der Lippe <[email protected]>
Reviewed-by: Paul Lewis <[email protected]>
diff --git a/front_end/externs.js b/front_end/externs.js
index f57724b..3a7d570 100644
--- a/front_end/externs.js
+++ b/front_end/externs.js
@@ -751,6 +751,8 @@
   /** @type {string} */
   this.type;
   /** @type {(!ESTree.Node|undefined)} */
+  this.key;
+  /** @type {(!ESTree.Node|undefined)} */
   this.body;
   /** @type {(!Array.<!ESTree.Node>|undefined)} */
   this.declarations;