IDL: make optional arguments (without default) explicit sometimes

Source/modules/filesystem/InspectorFileSystemAgent.cpp

 /*
  * Copyright (C) 2011, 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 454 matching lines @@
     toFileEntry(entry)->file(successCallback.release(), errorCallback.release());
 
     m_reader = FileReader::create(entry->filesystem()->executionContext());
     m_mimeType = MIMETypeRegistry::getMIMETypeForPath(entry->name());
 
     return true;
 }
 
 bool FileContentRequest::didGetFile(File* file)
 {
-    RefPtrWillBeRawPtr<Blob> blob = static_cast<Blob*>(file)->slice(m_start, m_end, IGNORE_EXCEPTION);
+    RefPtrWillBeRawPtr<Blob> blob = static_cast<Blob*>(file)->slice(m_start, makeOptional(m_end), String(), IGNORE_EXCEPTION);
     m_reader->setOnload(this);
     m_reader->setOnerror(this);
 
     m_reader->readAsArrayBuffer(blob.get(), IGNORE_EXCEPTION);
     return true;
 }
 
 void FileContentRequest::didRead()
 {
     RefPtr<ArrayBuffer> buffer = m_reader->arrayBufferResult();
@@ skipping 242 matching lines @@
     return 0;
 }
 
 void InspectorFileSystemAgent::trace(Visitor* visitor)
 {
     visitor->trace(m_page);
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink