Saving torrent file causes crash

[srirambv]

Description

Saving torrent file causes crash

Steps to Reproduce

1. Clean install 0.21.654
2. Visit https://webtorrent.io/torrents/big-buck-bunny.torrent
3. Click on save torrent, browser crashes

Actual result:

Expected result:
Shouldn't crash when saving torrent file

Reproduces how often:
100%

Brave Version

about:brave info:

Brave	0.21.654
OS Release	10.0.16299
Muon	5.1.3
V8	6.5.254.26
libchromiumcontent	65.0.3325.88
Node.js	7.9.0
rev	bc6272c
Update Channel	Beta
OS Platform	Microsoft Windows
OS Architecture	x64

Reproducible on current live release:
No

Additional Information

Saving an image doesn't cause crash
#13350
cc: @darkdh @bridiver

[bsclifton]

@darkdh possibly caused by the problem we had with bittorrent-tracker and it's downstream dependency on bufferutils. Maybe we can try removing the lock file and perform npm install using npm install --no-optional

[darkdh]

@bsclifton no, this is because item->GetWebContents() is null
https://github.com/brave/muon/blob/ac452600e5fc77e251155339ea9fb407469a14b6/atom/browser/atom_download_manager_delegate.cc#L139 so it sequentially cause null window and finally crash at window->inspectable_web_contents().
Only reproduced in C65

[ltilve]

It seems to be reproducible also on Linux and Mac.

[ltilve]

When file download was initiated by adding target="_blank" w/o download property, clicking that link was initiating file download from newly created tab instead of current tab that has that link.

When file download was controlled by download manager, newly created web contents was destroyed. However, brave was trying to find browser window's webcontents to show save dialog on it by using destroyed webcontents. But, it was already null, so can't find window pointer. It caused crash.

We created a PR to fix the issue brave/muon#522

It allows downloading from newly created tab crash to be handled too. In this patch, use last active native window if there is no window related with download item.

[ltilve]

Updated the PR to move download closing code from browser-laptop to muon. It seems AtomDownloadManagerDelegate is the proper place to do it because item's webcontents is used there and after used, we can close it safely.
#13404
brave/muon#522

[ltilve]

Created a new PR brave/muon#529 to amend the merged brave/muon#522. Just with the already applied patch, the tab would be closed whether it is newtab on download or not.

[ltilve]

Now that the muon PR is merged (brave/muon#529) the browser-laptop one #13404 could be merged too.

[bsclifton]

Fixed with brave/muon#529 and #13404

Thanks, @ltilve 😄 👍