fixup! Bug 41116: Normalize system fonts.

  gfxFontStyle fontStyle;

  nsAutoString systemFontName;

  if (aDocument->ShouldResistFingerprinting()) {

#ifdef XP_MACOSX

#if defined(XP_MACOSX)

    systemFontName = u"-apple-system"_ns;

    // Values taken from a macOS 10.15 system.

    switch (aFontID) {

      case LookAndFeel::FontID::Caption:

      case LookAndFeel::FontID::Menu:

        fontStyle.size = 13;

        break;

      case LookAndFeel::FontID::SmallCaption:

        fontStyle.weight = gfxFontStyle::FontWeight(700);

        // fall-through

      case LookAndFeel::FontID::MessageBox:

      case LookAndFeel::FontID::StatusBar:

        fontStyle.size = 11;

        break;

      default:

        fontStyle.size = 12;

        break;

    }

#elif defined(XP_WIN) || defined(MOZ_WIDGET_ANDROID)

    // Windows uses Segoe UI for Latin alphabets, but other fonts for some RTL

    // languages, so we fallback to sans-serif to fall back to the user's

    // default sans-serif. Size is 12px for all system fonts (tried in an en-US

    // system).

    // Several Android systems reported Roboto 12px, so similar to what Windows

    // does.

    systemFontName = u"sans-serif"_ns;

    fontStyle.size = 12;

#else

    // On Linux, there is not a default. For example, GNOME on Debian uses

    // Cantarell, 14.667px. Ubuntu Mate uses the Ubuntu font, but also 14.667px.

    // Fedora with KDE uses Noto Sans, 13.3333px, but it uses Noto Sans on

    // GNOME, too.

    // In general, Linux uses some sans-serif, but its size can vary between

    // 12px and 16px. We chose 15px because it is what Firefox is doing for the

    // UI font-size.

    systemFontName = u"sans-serif"_ns;

    fontStyle.size = 15;

#endif

  } else if (!LookAndFeel::GetFont(aFontID, systemFontName, fontStyle)) {

    return;