Downloading pdf files with the download button in the pdf viewer is stalling

This is one of the remaining issues of #21766 (moved): our external helper app dialog blocker leads to a stalled download using the download button on the pdf viewer. Right-clicking and using Save as... is still working, though.

mcs wrote in #21766 (moved):

We have not found a fix for the pdfjs download problem, but I think the reason our earlier fix is ineffective is because a blobURI is used for the download, and therefore the channel associated with the download cannot be suspended (suspend and resume are only implemented for some channel types). So in this case the suspend/resume solution won't work.