Mark the file downloaded from a blob as temporary
When emitting the BrowserExtension::openUrlRequest for the file a blob URL was downloaded to, add an entry to KParts::OpenArgumentRequest::metaData. This entry is taken into account by KonqMainWindow::openUrlRequestHelper which will set the tempFile flag of the KonqOpenUrlRequest it creates to true. This way, if the file is opened in Konqueror, it's deleted when the corresponding tab does. It doesn't have any effect if the file is opened in an external application.