stylo: Honor the relevant link visited pref.

MozReview-Commit-ID: D5NiEJUpONQ

components/layout_thread/lib.rs

@@ -594,6 +594,7 @@ impl LayoutThread {
                 stylist: &self.stylist,
                 options: StyleSystemOptions::default(),
                 guards: guards,
+                visited_styles_enabled: false,
                 running_animations: self.running_animations.clone(),
                 expired_animations: self.expired_animations.clone(),
                 local_context_creation_data: Mutex::new(thread_local_style_context_creation_data),

components/style/context.rs

@@ -117,6 +117,9 @@ pub struct SharedStyleContext<'a> {
     /// The CSS selector stylist.
     pub stylist: &'a Stylist,
 
+    /// Whether visited styles are enabled.
+    pub visited_styles_enabled: bool,
+
     /// Configuration options.
     pub options: StyleSystemOptions,
 

components/style/gecko/data.rs

@@ -187,6 +187,13 @@ impl PerDocumentStyleDataImpl {
         );
     }
 
+    /// Returns whether private browsing is enabled.
+    pub fn is_private_browsing_enabled(&self) -> bool {
+        let doc =
+            self.stylist.device().pres_context().mDocument.raw::<nsIDocument>();
+        unsafe { bindings::Gecko_IsPrivateBrowsingEnabled(doc) }
+    }
+
     /// Get the default computed values for this document.
     pub fn default_computed_values(&self) -> &Arc<ComputedValues> {
         self.stylist.device().default_computed_values_arc()

components/style/style_resolver.rs

@@ -12,7 +12,8 @@ use dom::TElement;
 use log::LogLevel::Trace;
 use matching::{CascadeVisitedMode, MatchMethods};
 use properties::{AnimationRules, CascadeFlags, ComputedValues};
-use properties::{IS_LINK, IS_ROOT_ELEMENT, IS_VISITED_LINK, PROHIBIT_DISPLAY_CONTENTS, SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP};
+use properties::{IS_LINK, IS_ROOT_ELEMENT, IS_VISITED_LINK};
+use properties::{PROHIBIT_DISPLAY_CONTENTS, SKIP_ROOT_AND_ITEM_BASED_DISPLAY_FIXUP};
 use properties::{VISITED_DEPENDENT_ONLY, cascade};
 use rule_tree::StrongRuleNode;
 use selector_parser::{PseudoElement, SelectorImpl};
@@ -476,7 +477,8 @@ where
 
         if pseudo.is_none() && self.element.is_link() {
             cascade_flags.insert(IS_LINK);
-            if self.element.is_visited_link() {
+            if self.element.is_visited_link() &&
+                self.context.shared.visited_styles_enabled {
                 cascade_flags.insert(IS_VISITED_LINK);
             }
         }

ports/geckolib/glue.rs

@@ -182,8 +182,13 @@ fn create_shared_context<'a>(global_style_data: &GlobalStyleData,
                              traversal_flags: TraversalFlags,
                              snapshot_map: &'a ServoElementSnapshotTable)
                              -> SharedStyleContext<'a> {
+    let visited_styles_enabled =
+        unsafe { bindings::Gecko_AreVisitedLinksEnabled() } &&
+        !per_doc_data.is_private_browsing_enabled();
+
     SharedStyleContext {
         stylist: &per_doc_data.stylist,
+        visited_styles_enabled: visited_styles_enabled,
         options: global_style_data.options.clone(),
         guards: StylesheetGuards::same(guard),
         timer: Timer::new(),