Follow up WebTorrent: Autoplay is sometimes blocked if media metadata is not ready yet

[btlechowski]

Follow up to #5471

Description

If the media element does not have metadata available immediately when the media viewer loads, then autoplay will fail with a DOMException.

Steps to Reproduce

1. Load the torrent from https://ia802608.us.archive.org/18/items/gd1975-06-17.aud.unknown.87560.flac16/gd1975-06-17.aud.unknown.87560.flac16_archive.torrent
2. Start the download.
3. Play a media file
4. The file should eventually start playing. There should be no warning that autoplay was blocked.
5. Close the playing audio and open another file.
6. Repeat steps 3 to 5.

Important: issue is fixed when added chrome-extension://lgjmpdmojkpocjcopdikifhejkkjglho/ into the auto play content settings per #5471 (comment)

Actual result:

Media sometimes does not autoplay.

Expected result:

Media should always autoplay.

Reproduces how often:

Intermittent issue

Brave	0.69.129 Chromium: 77.0.3865.90 (Official Build) (64-bit)
Revision	58c425ba843df2918d9d4b409331972646c393dd-refs/branch-heads/3865@{#830}
OS	Ubuntu 18.04 LTS

cc @brave/legacy_qa @feross @yrliou

[GeetaSarvadnya]

The issue is still reproducible in Windows 10 x64 - 0.69.130 continuously using STR mentioned in #5471 (comment)

#5471 (comment) - Issue is not reproducible