Auto merge of #17558 - ferjm:custompropmap.eq, r=emilio

Derive Eq and PartialEq for CustomPropertiesMap

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

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components/style/custom_properties.rs

@@ -97,7 +97,7 @@ impl ToCss for ComputedValue {
 /// DOM. CSSDeclarations expose property names as indexed properties, which
 /// need to be stable. So we keep an array of property names which order is
 /// determined on the order that they are added to the name-value map.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 pub struct CustomPropertiesMap {
     /// Custom property name index.
     index: Vec<Name>,
@@ -145,13 +145,6 @@ impl CustomPropertiesMap {
     }
 }
 
-impl Eq for CustomPropertiesMap {}
-impl PartialEq for CustomPropertiesMap {
-    fn eq(&self, other: &CustomPropertiesMap) -> bool {
-        self.values == other.values && self.index == other.index
-    }
-}
-
 impl ComputedValue {
     fn empty() -> ComputedValue {
         ComputedValue {