style: Add support for resolving default computed styles.

components/style/gecko/generated/bindings.rs

@@ -205,6 +205,7 @@ use gecko_bindings::structs::UpdateAnimationsTasks;
 use gecko_bindings::structs::ParsingMode;
 use gecko_bindings::structs::InheritTarget;
 use gecko_bindings::structs::URLMatchingFunction;
+use gecko_bindings::structs::StyleRuleInclusion;
 pub type nsTArrayBorrowed_uintptr_t<'a> = &'a mut ::gecko_bindings::structs::nsTArray<usize>;
 pub type RawServoStyleSetOwned = ::gecko_bindings::sugar::ownership::Owned<RawServoStyleSet>;
 pub type RawServoStyleSetOwnedOrNull = ::gecko_bindings::sugar::ownership::OwnedOrNull<RawServoStyleSet>;
@@ -2413,6 +2414,11 @@ extern "C" {
                                         target: InheritTarget)
      -> ServoComputedValuesStrong;
 }
+extern "C" {
+    pub fn Servo_ComputedValues_GetVisitedStyle(values:
+                                                    ServoComputedValuesBorrowed)
+     -> ServoComputedValuesStrong;
+}
 extern "C" {
     pub fn Servo_Initialize(dummy_url_data: *mut RawGeckoURLExtraData);
 }
@@ -2453,6 +2459,7 @@ extern "C" {
 extern "C" {
     pub fn Servo_ResolveStyleLazily(element: RawGeckoElementBorrowed,
                                     pseudo_type: CSSPseudoElementType,
+                                    rule_inclusion: StyleRuleInclusion,
                                     snapshots:
                                         *const ServoElementSnapshotTable,
                                     set: RawServoStyleSetBorrowed)

components/style/gecko/wrapper.rs

@@ -72,6 +72,8 @@ use std::cell::RefCell;
 use std::collections::HashMap;
 use std::fmt;
 use std::hash::{Hash, Hasher};
+use std::mem;
+use std::ops::DerefMut;
 use std::ptr;
 use string_cache::{Atom, Namespace, WeakAtom, WeakNamespace};
 use stylearc::Arc;
@@ -422,6 +424,29 @@ impl<'le> GeckoElement<'le> {
         }
     }
 
+    /// Sets the specified element data, return any existing data.
+    ///
+    /// Like `ensure_data`, only safe to call with exclusive access to the
+    /// element.
+    pub unsafe fn set_data(&self, replace_data: Option<ElementData>) -> Option<ElementData> {
+        match (self.get_data(), replace_data) {
+            (Some(old), Some(replace_data)) => {
+                Some(mem::replace(old.borrow_mut().deref_mut(), replace_data))
+            }
+            (Some(old), None) => {
+                let old_data = mem::replace(old.borrow_mut().deref_mut(), ElementData::new(None));
+                self.0.mServoData.set(ptr::null_mut());
+                Some(old_data)
+            }
+            (None, Some(replace_data)) => {
+                let ptr = Box::into_raw(Box::new(AtomicRefCell::new(replace_data)));
+                self.0.mServoData.set(ptr);
+                None
+            }
+            (None, None) => None,
+        }
+    }
+
     #[inline]
     fn has_id(&self) -> bool {
         self.as_node().get_bool_flag(nsINode_BooleanFlag::ElementHasID)