style: Move Ratio into independent files.

Based on https://drafts.csswg.org/css-values/#ratios, <ratio> should be
a general types in css values, and now the media query and the position use
this type, so let's move it into the independent files.

Differential Revision: https://phabricator.services.mozilla.com/D106218

components/style/values/computed/ratio.rs

@@ -0,0 +1,39 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `<ratio>` computed values.
+
+use crate::values::computed::NonNegativeNumber;
+use crate::values::generics::ratio::Ratio as GenericRatio;
+use crate::{One, Zero};
+use std::cmp::{Ordering, PartialOrd};
+
+/// A computed <ratio> value.
+pub type Ratio = GenericRatio<NonNegativeNumber>;
+
+impl PartialOrd for Ratio {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        f64::partial_cmp(
+            &((self.0).0 as f64 * (other.1).0 as f64),
+            &((self.1).0 as f64 * (other.0).0 as f64),
+        )
+    }
+}
+
+impl Ratio {
+    /// Returns a new Ratio.
+    pub fn new(a: f32, b: f32) -> Self {
+        GenericRatio(a.into(), b.into())
+    }
+
+    /// Returns the used value. A ratio of 0/0 behaves as the ratio 1/0.
+    /// https://drafts.csswg.org/css-values-4/#ratios
+    pub fn used_value(self) -> Self {
+        if self.0.is_zero() && self.1.is_zero() {
+            Ratio::new(One::one(), Zero::zero())
+        } else {
+            self
+        }
+    }
+}