Fire window.onerror for uncaught IndexedDB errors

LayoutTests/storage/indexeddb/resources/persistence.js

 if (this.importScripts) {
     importScripts('../../../resources/js-test.js');
     importScripts('shared.js');
 }
 
 description("Test IndexedDB persistence");
 
 indexedDBTest(prepareDatabase, unexpectedSuccessCallback);
 function prepareDatabase()
 {
     request = event.target;
     var db = request.result;
     var trans = request.transaction;
     trans.abort();
-    request.onerror = function() {
+    request.onerror = function(evt) {
+        evt.preventDefault();
         db.close();
         first();
     };
 }
 
 function first()
 {
     openAndChangeVersion(1, function (connection) {
         db = connection;
         shouldBe("db.version", "1");
@@ skipping 73 matching lines @@
     request.onupgradeneeded = function () {
         evalAndLog("db = request.result");
         shouldBeNonNull("db");
         callback(db);
     };
     request.onsuccess = function() {
         evalAndLog("db.close()");
         next();
     }
 }