IndexedDB: Rely on bindings for enum validation

Source/modules/indexeddb/IDBCursor.cpp

Index: Source/modules/indexeddb/IDBCursor.cpp
diff --git a/Source/modules/indexeddb/IDBCursor.cpp b/Source/modules/indexeddb/IDBCursor.cpp
index d26a7e11e2487b8f2f4ac399bed18a23735e29d1..ee01c33919af9c62a53dcc792d33666a884d6d9e 100644
--- a/Source/modules/indexeddb/IDBCursor.cpp
+++ b/Source/modules/indexeddb/IDBCursor.cpp
@@ -359,7 +359,7 @@ bool IDBCursor::isDeleted() const
     return m_source->idbIndex()->isDeleted();
 }
 
-WebIDBCursorDirection IDBCursor::stringToDirection(const String& directionString, ExceptionState& exceptionState)
+WebIDBCursorDirection IDBCursor::stringToDirection(const String& directionString)
 {
     if (directionString == IndexedDBNames::next)
         return WebIDBCursorDirectionNext;
@@ -370,7 +370,7 @@ WebIDBCursorDirection IDBCursor::stringToDirection(const String& directionString
     if (directionString == IndexedDBNames::prevunique)
         return WebIDBCursorDirectionPrevNoDuplicate;
 
-    exceptionState.throwTypeError("The direction provided ('" + directionString + "') is not one of 'next', 'nextunique', 'prev', or 'prevunique'.");
+    ASSERT_NOT_REACHED();
     return WebIDBCursorDirectionNext;
 }