Auto merge of #17236 - bradwerth:cloneRulesBetter, r=heycam

Define Gecko CounterStyle and FontFaceRule clone functions

<!-- Please describe your changes on the following line: -->
Defines and calls Gecko CounterStyle and FontFaceRule clone functions, protected by cfg directives to only apply in gecko builds.

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- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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components/style/gecko/generated/bindings.rs

@@ -1420,6 +1420,10 @@ extern "C" {
     pub fn Gecko_CSSFontFaceRule_Create(line: u32, column: u32)
      -> *mut nsCSSFontFaceRule;
 }
+extern "C" {
+    pub fn Gecko_CSSFontFaceRule_Clone(rule: *const nsCSSFontFaceRule)
+     -> *mut nsCSSFontFaceRule;
+}
 extern "C" {
     pub fn Gecko_CSSFontFaceRule_GetCssText(rule: *const nsCSSFontFaceRule,
                                             result: *mut nsAString);
@@ -1434,6 +1438,10 @@ extern "C" {
     pub fn Gecko_CSSCounterStyle_Create(name: *mut nsIAtom)
      -> *mut nsCSSCounterStyleRule;
 }
+extern "C" {
+    pub fn Gecko_CSSCounterStyle_Clone(rule: *const nsCSSCounterStyleRule)
+     -> *mut nsCSSCounterStyleRule;
+}
 extern "C" {
     pub fn Gecko_CSSCounterStyle_GetCssText(rule:
                                                 *const nsCSSCounterStyleRule,

components/style/gecko/rules.rs

@@ -150,6 +150,18 @@ impl ToNsCssValue for FontDisplay {
     }
 }
 
+impl FontFaceRule {
+    /// Ask Gecko to deep clone the nsCSSFontFaceRule, and then construct
+    /// a FontFaceRule object from it.
+    pub fn deep_clone_from_gecko(&self) -> FontFaceRule {
+        let result = unsafe {
+            UniqueRefPtr::from_addrefed(
+                bindings::Gecko_CSSFontFaceRule_Clone(self.get()))
+        };
+        result.get()
+    }
+}
+
 impl From<FontFaceRuleData> for FontFaceRule {
     fn from(data: FontFaceRuleData) -> FontFaceRule {
         let mut result = unsafe {
@@ -176,6 +188,18 @@ impl ToCssWithGuard for FontFaceRule {
 /// A @counter-style rule
 pub type CounterStyleRule = RefPtr<nsCSSCounterStyleRule>;
 
+impl CounterStyleRule {
+    /// Ask Gecko to deep clone the nsCSSCounterStyleRule, and then construct
+    /// a CounterStyleRule object from it.
+    pub fn deep_clone_from_gecko(&self) -> CounterStyleRule {
+        let result = unsafe {
+            UniqueRefPtr::from_addrefed(
+                bindings::Gecko_CSSCounterStyle_Clone(self.get()))
+        };
+        result.get()
+    }
+}
+
 impl From<counter_style::CounterStyleRuleData> for CounterStyleRule {
     fn from(data: counter_style::CounterStyleRuleData) -> CounterStyleRule {
         let mut result = unsafe {

components/style/stylesheets/counter_style_rule.rs

@@ -10,3 +10,15 @@
 pub use counter_style::CounterStyleRuleData as CounterStyleRule;
 #[cfg(feature = "gecko")]
 pub use gecko::rules::CounterStyleRule;
+
+impl CounterStyleRule {
+    #[cfg(feature = "servo")]
+    pub fn clone_conditionally_gecko_or_servo(&self) -> CounterStyleRule {
+        self.clone()
+    }
+
+    #[cfg(feature = "gecko")]
+    pub fn clone_conditionally_gecko_or_servo(&self) -> CounterStyleRule {
+        self.deep_clone_from_gecko()
+    }
+}

components/style/stylesheets/font_face_rule.rs

@@ -10,3 +10,15 @@
 pub use font_face::FontFaceRuleData as FontFaceRule;
 #[cfg(feature = "gecko")]
 pub use gecko::rules::FontFaceRule;
+
+impl FontFaceRule {
+    #[cfg(feature = "servo")]
+    pub fn clone_conditionally_gecko_or_servo(&self) -> FontFaceRule {
+        self.clone()
+    }
+
+    #[cfg(feature = "gecko")]
+    pub fn clone_conditionally_gecko_or_servo(&self) -> FontFaceRule {
+        self.deep_clone_from_gecko()
+    }
+}

components/style/stylesheets/mod.rs

@@ -289,11 +289,13 @@ impl DeepCloneWithLock for CssRule {
             },
             CssRule::FontFace(ref arc) => {
                 let rule = arc.read_with(guard);
-                CssRule::FontFace(Arc::new(lock.wrap(rule.clone())))
+                CssRule::FontFace(Arc::new(lock.wrap(
+                    rule.clone_conditionally_gecko_or_servo())))
             },
             CssRule::CounterStyle(ref arc) => {
                 let rule = arc.read_with(guard);
-                CssRule::CounterStyle(Arc::new(lock.wrap(rule.clone())))
+                CssRule::CounterStyle(Arc::new(lock.wrap(
+                    rule.clone_conditionally_gecko_or_servo())))
             },
             CssRule::Viewport(ref arc) => {
                 let rule = arc.read_with(guard);