style: Generalize moz-os-version into moz-platform

Allow differentiating non-windows platforms on it.

Differential Revision: https://phabricator.services.mozilla.com/D138431

components/style/gecko/media_features.rs

@@ -13,7 +13,6 @@ use crate::media_queries::{Device, MediaType};
 use crate::values::computed::CSSPixelLength;
 use crate::values::computed::Ratio;
 use crate::values::computed::Resolution;
-use crate::Atom;
 use app_units::Au;
 use euclid::default::Size2D;
 
@@ -550,20 +549,36 @@ fn eval_moz_is_resource_document(
     query_value.map_or(is_resource_doc, |v| v == is_resource_doc)
 }
 
-fn eval_moz_os_version(
-    device: &Device,
-    query_value: Option<Atom>,
-    _: Option<RangeOrOperator>,
-) -> bool {
+/// Allows front-end CSS to discern platform via media queries.
+#[derive(Clone, Copy, Debug, FromPrimitive, Parse, ToCss)]
+#[repr(u8)]
+pub enum Platform {
+    /// Matches any Android version.
+    Android,
+    /// For our purposes here, "linux" is just "gtk" (so unix-but-not-mac).
+    /// There's no need for our front-end code to differentiate between those
+    /// platforms and they already use the "linux" string elsewhere (e.g.,
+    /// toolkit/themes/linux).
+    Linux,
+    /// Matches any macOS version.
+    Macos,
+    /// Matches any Windows version.
+    Windows,
+    /// Matches only Windows 7.
+    WindowsWin7,
+    /// Matches only Windows 8.
+    WindowsWin8,
+    /// Matches windows 10 and actually matches windows 11 too, as of right now.
+    WindowsWin10,
+}
+
+fn eval_moz_platform(_: &Device, query_value: Option<Platform>) -> bool {
     let query_value = match query_value {
         Some(v) => v,
         None => return false,
     };
 
-    let os_version =
-        unsafe { bindings::Gecko_MediaFeatures_GetOperatingSystemVersion(device.document()) };
-
-    query_value.as_ptr() == os_version
+    unsafe { bindings::Gecko_MediaFeatures_MatchesPlatform(query_value) }
 }
 
 fn eval_moz_windows_non_native_menus(
@@ -576,7 +591,7 @@ fn eval_moz_windows_non_native_menus(
         0 => false,
         1 => true,
         _ => {
-            eval_moz_os_version(device, Some(atom!("windows-win10")), None) &&
+            eval_moz_platform(device, Some(Platform::WindowsWin10)) &&
                 get_lnf_int_as_bool(bindings::LookAndFeel_IntID::WindowsDefaultTheme as i32)
         },
     };
@@ -869,9 +884,9 @@ pub static MEDIA_FEATURES: [MediaFeatureDescription; 58] = [
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),
     feature!(
-        atom!("-moz-os-version"),
+        atom!("-moz-platform"),
         AllowsRanges::No,
-        Evaluator::Ident(eval_moz_os_version),
+        keyword_evaluator!(eval_moz_platform, Platform),
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),
     feature!(