When starting a download due to unsupportedContent being emitted, we
need to use (and later adopt) the page's QNetworkAccessManager.
Since we need the whole adopting logic for that case anyways, let's keep
things as they were and always run downloads in per-tab QNAMs.
This reverts 53e360ec4b and fixes#2134.
:hint all download does not use the response headers to determine the
filename (the prompt is shown before a request is even done), so our
long filename was pretty useless.
:hint works because it does a request first and uses the right filename,
but we need to wait until the prompt is shown before we can do
:prompt-open-download, since the request is a bit slower and would fail
otherwise.
The test was failing because of two reasons:
First, the old code had filename questions in DownloadManager.get and
DownloadManager.fetch which were almost identical, thus the part in
DownloadManager.get was removed in an earlier commit. All filename
asking is now done by DownloadManager.fetch. The good part is code
deduplication, the bad part is slightly modified behavior: The new code
doesn't wait for a filename to start the download, instead it tries to
fill the buffer immediately. This made the test fail because qute:// has
no registered handler, so in order for the test to pass now, the "no
crash" part is not enough, we also need to expect the "No handler"
error.
Secondly, and a rather rare (race) condition was the handling of errors
in the DownloadItem. If an error occured after the registration of
self.on_reply_error as error handler and before the check
reply.error() != QNetworkReply.NoError
at the end of the function, the error signal would be emitted twice:
Once by _die() (called by on_reply_error), and once by the init_reply
function directly (in the last if block). This lead to duplicated error
messages. This is also explained in a comment in the file (with small
"stack traces").
