WPT: Update IDB WPT helper to avoid duplicate object store creation

In the WPT that requires creating IDB connection with different version,
we should not create the same object store for multiple times. This CL adds
a version check to ensure that it's only created when version equals to 1.

Bug: 1331187
Change-Id: I4d52cc0e2c56493db5bad59705822c3550fa886c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4178503
Reviewed-by: Fergal Daly <fergal@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1107329}

IndexedDB/resources/support.js

@@ -216,7 +216,10 @@ async function createIndexedDBForTesting(rc, dbName, version) {
   await rc.executeScript((dbName, version) => {
     let request = indexedDB.open(dbName, version);
     request.onupgradeneeded = () => {
-      request.result.createObjectStore('store');
+      if (version == 1) {
+        // Only create the object store once.
+        request.result.createObjectStore('store');
+      }
     }
     request.onversionchange = () => {
       fail(t, 'unexpectedly received versionchange event.');