Onerror return value handling in workers fixed as per HTML5 spec.

LayoutTests/storage/indexeddb/resources/transaction-complete-workers.js

 if (this.importScripts) {
     importScripts('../../../resources/js-test.js');
     importScripts('shared.js');
 }
 
 description("Test IndexedDB workers, recursion, and transaction termination.");
 
 indexedDBTest(prepareDatabase, createTransaction);
 function prepareDatabase(evt)
 {
@@ skipping 87 matching lines @@
     debug("");
     debug("errorHandler():");
     // FIXME: Should be able to stop the error here, but it isn't an Event object.
     // evalAndLog("event.preventDefault()");
     evalAndLog("self.onerror = self.old_onerror");
     evalAndLog("transaction = db.transaction('store')");
     evalAndLog("store = transaction.objectStore('store')");
     transaction.onerror = unexpectedErrorCallback;
     transaction.onabort = unexpectedAbortCallback;
     transaction.oncomplete = errorTransactionCompleted;
+    // We will cancel the error event here itself,
+    // this will allow the transaction to complete.
+    // Thus the event.preventDefault in the worker.onerror
+    // is no longer required in this scenario.
+    return true;
 }
 
 function errorTransactionCompleted()
 {
     testPassed("Transaction completed");
     evalAndExpectException("store.get(0)", "0", "'TransactionInactiveError'");
     finishJSTest();
 }