Auto merge of #17028 - bradwerth:innerClone, r=heycam

Stylo: Deep clone ServoStyleSheets.

MozReview-Commit-ID: 6hYIcOa86Y

<!-- Please describe your changes on the following line: -->
https://bugzilla.mozilla.org/show_bug.cgi?id=1339629
https://reviewboard.mozilla.org/r/135314/

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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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- [ ] These changes do not require tests because _____

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9 files changed, 221 insertions, 10 deletions

diff --git a/components/style/counter_style/mod.rs b/components/style/counter_style/mod.rs
index b1c461b4301..20cd638b758 100644
--- a/components/style/counter_style/mod.rs
+++ b/components/style/counter_style/mod.rs
@@ -142,7 +142,7 @@ macro_rules! counter_style_descriptors {
         $( #[$doc: meta] $name: tt $ident: ident / $gecko_ident: ident: $ty: ty = $initial: tt )+
     ) => {
         /// An @counter-style rule
-        #[derive(Debug)]
+        #[derive(Clone, Debug)]
         pub struct CounterStyleRuleData {
             name: CustomIdent,
             $(
diff --git a/components/style/document_condition.rs b/components/style/document_condition.rs
index aef034f2eeb..b4e89adcce7 100644
--- a/components/style/document_condition.rs
+++ b/components/style/document_condition.rs
@@ -20,7 +20,7 @@ use style_traits::ToCss;
 use values::specified::url::SpecifiedUrl;
 
 /// A URL matching function for a `@document` rule's condition.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub enum UrlMatchingFunction {
     /// Exact URL matching function. It evaluates to true whenever the
     /// URL of the document being styled is exactly the URL given.
@@ -141,7 +141,7 @@ impl ToCss for UrlMatchingFunction {
 /// The `@document` rule's condition is written as a comma-separated list of
 /// URL matching functions, and the condition evaluates to true whenever any
 /// one of those functions evaluates to true.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct DocumentCondition(Vec<UrlMatchingFunction>);
 
 impl DocumentCondition {
diff --git a/components/style/font_face.rs b/components/style/font_face.rs
index 4c953c3b028..439642f68c9 100644
--- a/components/style/font_face.rs
+++ b/components/style/font_face.rs
@@ -194,7 +194,7 @@ macro_rules! font_face_descriptors_common {
         /// Data inside a `@font-face` rule.
         ///
         /// https://drafts.csswg.org/css-fonts/#font-face-rule
-        #[derive(Debug, PartialEq, Eq)]
+        #[derive(Clone, Debug, PartialEq, Eq)]
         pub struct FontFaceRuleData {
             $(
                 #[$doc]
diff --git a/components/style/gecko/generated/bindings.rs b/components/style/gecko/generated/bindings.rs
index 028b4678c3f..a03c8ff8feb 100644
--- a/components/style/gecko/generated/bindings.rs
+++ b/components/style/gecko/generated/bindings.rs
@@ -1737,6 +1737,10 @@ extern "C" {
      -> ServoCssRulesStrong;
 }
 extern "C" {
+    pub fn Servo_StyleSheet_Clone(sheet: RawServoStyleSheetBorrowed)
+     -> RawServoStyleSheetStrong;
+}
+extern "C" {
     pub fn Servo_StyleSet_Init(pres_context: RawGeckoPresContextOwned)
      -> RawServoStyleSetOwned;
 }
diff --git a/components/style/keyframes.rs b/components/style/keyframes.rs
index db60c86aa9e..e0c589a1c32 100644
--- a/components/style/keyframes.rs
+++ b/components/style/keyframes.rs
@@ -71,7 +71,7 @@ impl KeyframePercentage {
 
 /// A keyframes selector is a list of percentages or from/to symbols, which are
 /// converted at parse time to percentages.
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct KeyframeSelector(Vec<KeyframePercentage>);
 
 impl ToCss for KeyframeSelector {
@@ -150,6 +150,16 @@ impl Keyframe {
         };
         parse_one_rule(&mut input, &mut rule_parser)
     }
+
+    /// Deep clones this Keyframe.
+    pub fn deep_clone_with_lock(&self,
+                                lock: &SharedRwLock) -> Keyframe {
+        let guard = lock.read();
+        Keyframe {
+            selector: self.selector.clone(),
+            block: Arc::new(lock.wrap(self.block.read_with(&guard).clone())),
+        }
+    }
 }
 
 /// A keyframes step value. This can be a synthetised keyframes animation, that
diff --git a/components/style/stylesheets.rs b/components/style/stylesheets.rs
index 2c55c73fd8d..81a5fbc98dd 100644
--- a/components/style/stylesheets.rs
+++ b/components/style/stylesheets.rs
@@ -37,6 +37,7 @@ use servo_config::prefs::PREFS;
 #[cfg(not(feature = "gecko"))]
 use servo_url::ServoUrl;
 use shared_lock::{SharedRwLock, Locked, ToCssWithGuard, SharedRwLockReadGuard};
+use std::borrow::Borrow;
 use std::cell::Cell;
 use std::fmt;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -91,7 +92,7 @@ pub enum Origin {
 }
 
 /// A set of namespaces applying to a given stylesheet.
-#[derive(Default, Debug)]
+#[derive(Clone, Default, Debug)]
 #[allow(missing_docs)]
 pub struct Namespaces {
     pub default: Option<Namespace>,
@@ -107,6 +108,15 @@ impl CssRules {
     pub fn is_empty(&self) -> bool {
         self.0.is_empty()
     }
+
+    /// Creates a deep clone where each CssRule has also been cloned with
+    /// the provided lock.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> CssRules {
+        CssRules(
+            self.0.iter().map(|ref x| x.deep_clone_with_lock(lock)).collect()
+        )
+    }
 }
 
 #[allow(missing_docs)]
@@ -469,6 +479,64 @@ impl CssRule {
             }
         }
     }
+
+    /// Deep clones this CssRule.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> CssRule {
+        let guard = lock.read();
+        match *self {
+            CssRule::Namespace(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Namespace(Arc::new(lock.wrap(rule.clone())))
+            },
+            CssRule::Import(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Import(Arc::new(lock.wrap(rule.clone())))
+            },
+            CssRule::Style(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Style(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+            CssRule::Media(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Media(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+            CssRule::FontFace(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::FontFace(Arc::new(lock.wrap(rule.clone())))
+            },
+            CssRule::CounterStyle(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::CounterStyle(Arc::new(lock.wrap(rule.clone())))
+            },
+            CssRule::Viewport(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Viewport(Arc::new(lock.wrap(rule.clone())))
+            },
+            CssRule::Keyframes(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Keyframes(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+            CssRule::Supports(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Supports(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+            CssRule::Page(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Page(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+            CssRule::Document(ref arc) => {
+                let rule = arc.read_with(&guard);
+                CssRule::Document(Arc::new(
+                    lock.wrap(rule.deep_clone_with_lock(lock))))
+            },
+        }
+    }
 }
 
 impl ToCssWithGuard for CssRule {
@@ -500,7 +568,7 @@ fn get_location_with_offset(location: SourceLocation, offset: u64)
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 #[allow(missing_docs)]
 pub struct NamespaceRule {
     /// `None` for the default Namespace
@@ -540,6 +608,16 @@ pub struct ImportRule {
     pub stylesheet: Arc<Stylesheet>,
 }
 
+impl Clone for ImportRule {
+    fn clone(&self) -> ImportRule {
+        let stylesheet: &Stylesheet = self.stylesheet.borrow();
+        ImportRule {
+            url: self.url.clone(),
+            stylesheet: Arc::new(stylesheet.clone()),
+        }
+    }
+}
+
 impl ToCssWithGuard for ImportRule {
     fn to_css<W>(&self, guard: &SharedRwLockReadGuard, dest: &mut W) -> fmt::Result
     where W: fmt::Write {
@@ -604,6 +682,23 @@ impl KeyframesRule {
     }
 }
 
+impl KeyframesRule {
+    /// Deep clones this KeyframesRule.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> KeyframesRule {
+        let guard = lock.read();
+        KeyframesRule {
+            name: self.name.clone(),
+            keyframes: self.keyframes.iter()
+                .map(|ref x| Arc::new(lock.wrap(
+                    x.read_with(&guard).deep_clone_with_lock(lock))))
+                .collect(),
+            vendor_prefix: self.vendor_prefix.clone(),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 #[allow(missing_docs)]
 #[derive(Debug)]
 pub struct MediaRule {
@@ -628,6 +723,21 @@ impl ToCssWithGuard for MediaRule {
     }
 }
 
+impl MediaRule {
+    /// Deep clones this MediaRule.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> MediaRule {
+        let guard = lock.read();
+        let media_queries = self.media_queries.read_with(&guard);
+        let rules = self.rules.read_with(&guard);
+        MediaRule {
+            media_queries: Arc::new(lock.wrap(media_queries.clone())),
+            rules: Arc::new(lock.wrap(rules.deep_clone_with_lock(lock))),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 
 #[derive(Debug)]
 /// An @supports rule
@@ -656,6 +766,20 @@ impl ToCssWithGuard for SupportsRule {
     }
 }
 
+impl SupportsRule {
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> SupportsRule {
+        let guard = lock.read();
+        let rules = self.rules.read_with(&guard);
+        SupportsRule {
+            condition: self.condition.clone(),
+            rules: Arc::new(lock.wrap(rules.deep_clone_with_lock(lock))),
+            enabled: self.enabled,
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 /// A [`@page`][page] rule.  This implements only a limited subset of the CSS 2.2 syntax.  In this
 /// subset, [page selectors][page-selectors] are not implemented.
 ///
@@ -682,6 +806,17 @@ impl ToCssWithGuard for PageRule {
     }
 }
 
+impl PageRule {
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> PageRule {
+        let guard = lock.read();
+        PageRule {
+            block: Arc::new(lock.wrap(self.block.read_with(&guard).clone())),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 #[allow(missing_docs)]
 #[derive(Debug)]
 pub struct StyleRule {
@@ -711,6 +846,19 @@ impl ToCssWithGuard for StyleRule {
     }
 }
 
+impl StyleRule {
+    /// Deep clones this StyleRule.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> StyleRule {
+        let guard = lock.read();
+        StyleRule {
+            selectors: self.selectors.clone(),
+            block: Arc::new(lock.wrap(self.block.read_with(&guard).clone())),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 /// A @font-face rule
 #[cfg(feature = "servo")]
 pub type FontFaceRule = FontFaceRuleData;
@@ -744,6 +892,20 @@ impl ToCssWithGuard for DocumentRule {
     }
 }
 
+impl DocumentRule {
+    /// Deep clones this DocumentRule.
+    fn deep_clone_with_lock(&self,
+                            lock: &SharedRwLock) -> DocumentRule {
+        let guard = lock.read();
+        let rules = self.rules.read_with(&guard);
+        DocumentRule {
+            condition: self.condition.clone(),
+            rules: Arc::new(lock.wrap(rules.deep_clone_with_lock(lock))),
+            source_location: self.source_location.clone(),
+        }
+    }
+}
+
 impl Stylesheet {
     /// Updates an empty stylesheet from a given string of text.
     pub fn update_from_str(existing: &Stylesheet,
@@ -901,6 +1063,35 @@ impl Stylesheet {
     }
 }
 
+impl Clone for Stylesheet {
+    fn clone(&self) -> Stylesheet {
+        // Create a new lock for our clone.
+        let lock = self.shared_lock.clone();
+        let guard = self.shared_lock.read();
+
+        // Make a deep clone of the rules, using the new lock.
+        let rules = self.rules.read_with(&guard);
+        let cloned_rules = rules.deep_clone_with_lock(&lock);
+
+        // Make a deep clone of the media, using the new lock.
+        let media = self.media.read_with(&guard);
+        let cloned_media = media.clone();
+
+        Stylesheet {
+            rules: Arc::new(lock.wrap(cloned_rules)),
+            media: Arc::new(lock.wrap(cloned_media)),
+            origin: self.origin,
+            url_data: self.url_data.clone(),
+            shared_lock: lock,
+            namespaces: RwLock::new((*self.namespaces.read()).clone()),
+            dirty_on_viewport_size_change: AtomicBool::new(
+                self.dirty_on_viewport_size_change.load(Ordering::SeqCst)),
+            disabled: AtomicBool::new(self.disabled.load(Ordering::SeqCst)),
+            quirks_mode: self.quirks_mode,
+        }
+    }
+}
+
 fn effective_rules<F>(rules: &[CssRule],
                       device: &Device,
                       quirks_mode: QuirksMode,
diff --git a/components/style/supports.rs b/components/style/supports.rs
index 3b651ba9264..9b297963056 100644
--- a/components/style/supports.rs
+++ b/components/style/supports.rs
@@ -11,7 +11,7 @@ use std::fmt;
 use style_traits::ToCss;
 use stylesheets::CssRuleType;
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 /// An @supports condition
 ///
 /// https://drafts.csswg.org/css-conditional-3/#at-supports
@@ -162,7 +162,7 @@ impl ToCss for SupportsCondition {
     }
 }
 
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 /// A possibly-invalid property declaration
 pub struct Declaration {
     /// The property name
diff --git a/components/style/viewport.rs b/components/style/viewport.rs
index 0953d9a4b7a..68ea6a3033f 100644
--- a/components/style/viewport.rs
+++ b/components/style/viewport.rs
@@ -309,7 +309,7 @@ impl<'a, 'b> DeclarationParser for ViewportRuleParser<'a, 'b> {
 }
 
 /// A `@viewport` rule.
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct ViewportRule {
     /// The declarations contained in this @viewport rule.
diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 401cdac1a1f..0614858ad7a 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -792,6 +792,12 @@ pub extern "C" fn Servo_StyleSheet_GetRules(sheet: RawServoStyleSheetBorrowed) -
     Stylesheet::as_arc(&sheet).rules.clone().into_strong()
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_StyleSheet_Clone(raw_sheet: RawServoStyleSheetBorrowed) -> RawServoStyleSheetStrong {
+    let sheet: &Arc<Stylesheet> = HasArcFFI::as_arc(&raw_sheet);
+    Arc::new(sheet.as_ref().clone()).into_strong()
+}
+
 fn read_locked_arc<T, R, F>(raw: &<Locked<T> as HasFFI>::FFIType, func: F) -> R
     where Locked<T>: HasArcFFI, F: FnOnce(&T) -> R
 {