Auto merge of #16698 - bradwerth:cloneRight, r=heycam

Change StyleSet to track stylesheets by unique ID.

MozReview-Commit-ID: Ky3P53o4Euw

https://bugzilla.mozilla.org/show_bug.cgi?id=1348481
https://reviewboard.mozilla.org/r/128850/

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- [ ] These changes fix #__ (github issue number if applicable).

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1 files changed, 44 insertions, 23 deletions

diff --git a/components/style/stylesheet_set.rs b/components/style/stylesheet_set.rs
index e1f782bbbbf..78e0c9cd558 100644
--- a/components/style/stylesheet_set.rs
+++ b/components/style/stylesheet_set.rs
@@ -4,19 +4,26 @@
 
 //! A centralized set of stylesheets for a document.
 
-use arc_ptr_eq;
 use std::sync::Arc;
 use stylesheets::Stylesheet;
 
+/// Entry for a StylesheetSet. We don't bother creating a constructor, because
+/// there's no sensible defaults for the member variables.
+pub struct StylesheetSetEntry {
+    unique_id: u32,
+    sheet: Arc<Stylesheet>,
+}
+
 /// The set of stylesheets effective for a given document.
 pub struct StylesheetSet {
-    /// The actual list of all the stylesheets that apply to the given document.
+    /// The actual list of all the stylesheets that apply to the given document,
+    /// each stylesheet associated with a unique ID.
     ///
     /// This is only a list of top-level stylesheets, and as such it doesn't
     /// include recursive `@import` rules.
-    stylesheets: Vec<Arc<Stylesheet>>,
+    entries: Vec<StylesheetSetEntry>,
 
-    /// Whether the stylesheets list above has changed since the last restyle.
+    /// Whether the entries list above has changed since the last restyle.
     dirty: bool,
 
     /// Has author style been disabled?
@@ -27,7 +34,7 @@ impl StylesheetSet {
     /// Create a new empty StylesheetSet.
     pub fn new() -> Self {
         StylesheetSet {
-            stylesheets: vec![],
+            entries: vec![],
             dirty: false,
             author_style_disabled: false,
         }
@@ -39,39 +46,51 @@ impl StylesheetSet {
         self.author_style_disabled
     }
 
-    fn remove_stylesheet_if_present(&mut self, sheet: &Arc<Stylesheet>) {
-        self.stylesheets.retain(|x| !arc_ptr_eq(x, sheet));
+    fn remove_stylesheet_if_present(&mut self, unique_id: u32) {
+        self.entries.retain(|x| x.unique_id != unique_id);
     }
 
     /// Appends a new stylesheet to the current set.
-    pub fn append_stylesheet(&mut self, sheet: &Arc<Stylesheet>) {
-        self.remove_stylesheet_if_present(sheet);
-        self.stylesheets.push(sheet.clone());
+    pub fn append_stylesheet(&mut self, sheet: &Arc<Stylesheet>,
+                             unique_id: u32) {
+        self.remove_stylesheet_if_present(unique_id);
+        self.entries.push(StylesheetSetEntry {
+            unique_id: unique_id,
+            sheet: sheet.clone(),
+        });
         self.dirty = true;
     }
 
     /// Prepend a new stylesheet to the current set.
-    pub fn prepend_stylesheet(&mut self, sheet: &Arc<Stylesheet>) {
-        self.remove_stylesheet_if_present(sheet);
-        self.stylesheets.insert(0, sheet.clone());
+    pub fn prepend_stylesheet(&mut self, sheet: &Arc<Stylesheet>,
+                              unique_id: u32) {
+        self.remove_stylesheet_if_present(unique_id);
+        self.entries.insert(0, StylesheetSetEntry {
+            unique_id: unique_id,
+            sheet: sheet.clone(),
+        });
         self.dirty = true;
     }
 
     /// Insert a given stylesheet before another stylesheet in the document.
     pub fn insert_stylesheet_before(&mut self,
                                     sheet: &Arc<Stylesheet>,
-                                    before: &Arc<Stylesheet>) {
-        self.remove_stylesheet_if_present(sheet);
-        let index = self.stylesheets.iter().position(|x| {
-            arc_ptr_eq(x, before)
-        }).expect("`before` stylesheet not found");
-        self.stylesheets.insert(index, sheet.clone());
+                                    unique_id: u32,
+                                    before_unique_id: u32) {
+        self.remove_stylesheet_if_present(unique_id);
+        let index = self.entries.iter().position(|x| {
+            x.unique_id == before_unique_id
+        }).expect("`before_unique_id` stylesheet not found");
+        self.entries.insert(index, StylesheetSetEntry {
+            unique_id: unique_id,
+            sheet: sheet.clone(),
+        });
         self.dirty = true;
     }
 
     /// Remove a given stylesheet from the set.
-    pub fn remove_stylesheet(&mut self, sheet: &Arc<Stylesheet>) {
-        self.remove_stylesheet_if_present(sheet);
+    pub fn remove_stylesheet(&mut self, unique_id: u32) {
+        self.remove_stylesheet_if_present(unique_id);
         self.dirty = true;
     }
 
@@ -90,9 +109,11 @@ impl StylesheetSet {
     }
 
     /// Flush the current set, unmarking it as dirty.
-    pub fn flush(&mut self) -> &[Arc<Stylesheet>] {
+    pub fn flush(&mut self, sheets: &mut Vec<Arc<Stylesheet>>) {
         self.dirty = false;
-        &self.stylesheets
+        for entry in &self.entries {
+            sheets.push(entry.sheet.clone())
+        }
     }
 
     /// Mark the stylesheets as dirty, because something external may have