Fix horrible jitter when selecting pivot table

Bug: b/289957407
Change-Id: I21778f234dd257145e14ce708383e1f6ad1d42e8
diff --git a/ui/src/controller/pivot_table_controller.ts b/ui/src/controller/pivot_table_controller.ts
index e91ec98..e8492df 100644
--- a/ui/src/controller/pivot_table_controller.ts
+++ b/ui/src/controller/pivot_table_controller.ts
@@ -197,7 +197,7 @@
     }
 
     // ES6 Set does not have .every method, only Array does.
-    for (const track in tracks) {
+    for (const track of tracks) {
       if (!this.lastQueryAreaTracks.has(track)) {
         return false;
       }