PDF files can not be previewed with the BE module

[hannesbochmann]

When clicking on a thumbnail of a PDF file, the following error occurs:

Core: Exception handler (WEB): Uncaught TYPO3 Exception: Call to undefined method TYPO3\CMS\Core\Resource\ResourceStorage::dumpFileContents() | Error thrown in file .../media/Classes/Controller/AssetController.php in line 88.

The method dumpFileContents() needs to be replaced with streamFile(). Furhtermore the response needs to be send like \TYPO3\CMS\Core\Http\AbstractApplication::sendResponse() does.