Add support for Google Widevine for Netflix support

[bbondy]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Test Plan:

• Test that netflix gives you a prompt to enable in preferences.
• Test that Windows and macOS can play netflix.com with a prompt after enabling in preferences.
• Test that Linux doesn't allow you to turn it on.

Fix #468

Auditors: @diracdeltas

[bbondy]

@diracdeltas I'm merging for now for testing's sake but please review and I'll do things in a follow up. Thanks!

[bbondy]

@diracdeltas screenshots here to see a play by play visually before reviewing:
#468 (comment)

[diracdeltas]

lgtm