Use IDL argument default values in modules/indexeddb/

Source/modules/indexeddb/IDBCursor.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 374 matching lines @@
     ASSERT(m_request || !m_blobInfo || !m_blobInfo->size());
     if (m_blobInfo.get() && m_blobInfo->size()) {
         ASSERT(m_request);
         m_transaction->db()->ackReceivedBlobs(m_blobInfo.get());
         m_blobInfo.clear();
     }
 }
 
 blink::WebIDBCursorDirection IDBCursor::stringToDirection(const String& directionString, ExceptionState& exceptionState)
 {
-    if (directionString.isNull() || directionString == IDBCursor::directionNext())
+    if (directionString == IDBCursor::directionNext())
         return blink::WebIDBCursorDirectionNext;
     if (directionString == IDBCursor::directionNextUnique())
         return blink::WebIDBCursorDirectionNextNoDuplicate;
     if (directionString == IDBCursor::directionPrev())
         return blink::WebIDBCursorDirectionPrev;
     if (directionString == IDBCursor::directionPrevUnique())
         return blink::WebIDBCursorDirectionPrevNoDuplicate;
 
     exceptionState.throwTypeError("The direction provided ('" + directionString + "') is not one of 'next', 'nextunique', 'prev', or 'prevunique'.");
     return blink::WebIDBCursorDirectionNext;
@@ skipping 14 matching lines @@
     case blink::WebIDBCursorDirectionPrevNoDuplicate:
         return IDBCursor::directionPrevUnique();
 
     default:
         ASSERT_NOT_REACHED();
         return IDBCursor::directionNext();
     }
 }
 
 } // namespace WebCore