Torrents are fully downloaded to memory, potential OOM

[btlechowski]

Steps to Reproduce

1. Go to https://webtorrent.io/free-torrents
2. Click on Tears of Steel magnet link
3. Start downloading the torrent and observe brave memory usage

Actual result:

Torrent is fully downloaded to memory. Even when torrent is finished downloading, memory is not released. It is released only when the torrent tab is closed and the media associated with it is closed.

Tears of Steel has 571 MB.

Expected result:

Torrent content is periodically written to disk.

Reproduces how often:

always

Brave version (chrome://version info)

Brave	0.55.5 Chromium: 70.0.3538.16 (Official Build) dev (64-bit)
Revision	16ed95b41bb05e565b11fb66ac33c660b721f778-refs/branch-heads/3538@{#306}
OS	Windows 7

cc @yrliou @bridiver

Related issues: #289 #855

[kjozwiak]

Great catch @btlechowski 👍

[Brave-Matt]

Just had a reddit user report this:
https://www.reddit.com/r/brave_browser/comments/9swo0b/whats_the_path_of_downloaded_files_throught/

[tildelowengrimm]

This looks like a dupe of #1199.