IndexedDB: Rely on bindings for enum validation

Source/modules/indexeddb/IDBTransaction.cpp

Index: Source/modules/indexeddb/IDBTransaction.cpp
diff --git a/Source/modules/indexeddb/IDBTransaction.cpp b/Source/modules/indexeddb/IDBTransaction.cpp
index c8df341edde5e533a73441f2d66bda96b70bf3de..305cf03bb2a421849c026fb616293406d9616221 100644
--- a/Source/modules/indexeddb/IDBTransaction.cpp
+++ b/Source/modules/indexeddb/IDBTransaction.cpp
@@ -299,14 +299,15 @@ bool IDBTransaction::hasPendingActivity() const
     return m_hasPendingActivity && !m_contextStopped;
 }
 
-WebIDBTransactionMode IDBTransaction::stringToMode(const String& modeString, ExceptionState& exceptionState)
+WebIDBTransactionMode IDBTransaction::stringToMode(const String& modeString)
 {
     if (modeString == IndexedDBNames::readonly)
         return WebIDBTransactionModeReadOnly;
     if (modeString == IndexedDBNames::readwrite)
         return WebIDBTransactionModeReadWrite;
-
-    exceptionState.throwTypeError("The mode provided ('" + modeString + "') is not one of 'readonly' or 'readwrite'.");
+    if (modeString == IndexedDBNames::versionchange)
+        return WebIDBTransactionModeVersionChange;
+    ASSERT_NOT_REACHED();
     return WebIDBTransactionModeReadOnly;
 }