Automatic dark theme doesn't work #63830
Description
Requested in #61079 and implemented in #61236, the automatic theme switching doesn't seem to do anything: If I visit https://doc.rust-lang.org/nightly/std/ while the system is in dark mode, I can see in the developer tools that the <html> element has the style content: "dark";, but the page is still showing as the light theme. Local storage is empty for doc.rust-lang.org, and the issue affects private windows as well.
Tested on:
- Firefox 68.0.2 on macOS 10.14.6
- Firefox 68.0.2 on Windows 10
- Chrome 76.0.3809.100 on Windows 10