Update CSS animations in a SequentialTask.

We create the SequentialTask only if:

* We have no old computed values and we have animation name style in the new
  computed values.
* Any animation properties is changed.
* display property is changed from 'none' and we have animation name style.
* display property is changed to 'none'.

In a subsequent patch we skip the SequentialTask if we have no running
animations and the display propery is changed to 'none'.

components/script/layout_wrapper.rs

@@ -446,6 +446,10 @@ impl<'le> TElement for ServoLayoutElement<'le> {
     fn has_selector_flags(&self, flags: ElementSelectorFlags) -> bool {
         self.element.has_selector_flags(flags)
     }
+
+    fn update_animations(&self, _pseudo: Option<&PseudoElement>) {
+        panic!("this should be only called on gecko");
+    }
 }
 
 impl<'le> PartialEq for ServoLayoutElement<'le> {

components/style/context.rs

@@ -15,6 +15,7 @@ use euclid::Size2D;
 use matching::StyleSharingCandidateCache;
 use parking_lot::RwLock;
 use properties::ComputedValues;
+use selector_parser::PseudoElement;
 use selectors::matching::ElementSelectorFlags;
 use servo_config::opts;
 use std::collections::HashMap;
@@ -181,6 +182,10 @@ pub enum SequentialTask<E: TElement> {
     /// Sets selector flags. This is used when we need to set flags on an
     /// element that we don't have exclusive access to (i.e. the parent).
     SetSelectorFlags(SendElement<E>, ElementSelectorFlags),
+
+    /// Marks that we need to create/remove/update CSS animations after the
+    /// first traversal.
+    UpdateAnimations(SendElement<E>, Option<PseudoElement>),
 }
 
 impl<E: TElement> SequentialTask<E> {
@@ -192,6 +197,9 @@ impl<E: TElement> SequentialTask<E> {
             SetSelectorFlags(el, flags) => {
                 unsafe { el.set_selector_flags(flags) };
             }
+            UpdateAnimations(el, pseudo) => {
+                unsafe { el.update_animations(pseudo.as_ref()) };
+            }
         }
     }
 
@@ -200,6 +208,12 @@ impl<E: TElement> SequentialTask<E> {
         use self::SequentialTask::*;
         SetSelectorFlags(unsafe { SendElement::new(el) }, flags)
     }
+
+    /// Creates a task to update CSS Animations on a given (pseudo-)element.
+    pub fn update_animations(el: E, pseudo: Option<PseudoElement>) -> Self {
+        use self::SequentialTask::*;
+        UpdateAnimations(unsafe { SendElement::new(el) }, pseudo)
+    }
 }
 
 /// A thread-local style context.

components/style/dom.rs

@@ -335,6 +335,10 @@ pub trait TElement : PartialEq + Debug + Sized + Copy + Clone + ElementExt + Pre
 
     /// Returns true if the element has all the specified selector flags.
     fn has_selector_flags(&self, flags: ElementSelectorFlags) -> bool;
+
+    /// Creates a task to update CSS Animations on a given (pseudo-)element.
+    /// Note: Gecko only.
+    fn update_animations(&self, _pseudo: Option<&PseudoElement>);
 }
 
 /// TNode and TElement aren't Send because we want to be careful and explicit

components/style/gecko/wrapper.rs

@@ -33,12 +33,14 @@ use gecko_bindings::bindings::Gecko_GetAnimationRule;
 use gecko_bindings::bindings::Gecko_GetHTMLPresentationAttrDeclarationBlock;
 use gecko_bindings::bindings::Gecko_GetStyleAttrDeclarationBlock;
 use gecko_bindings::bindings::Gecko_GetStyleContext;
+use gecko_bindings::bindings::Gecko_UpdateAnimations;
 use gecko_bindings::structs;
 use gecko_bindings::structs::{RawGeckoElement, RawGeckoNode};
 use gecko_bindings::structs::{nsIAtom, nsIContent, nsStyleContext};
 use gecko_bindings::structs::EffectCompositor_CascadeLevel as CascadeLevel;
 use gecko_bindings::structs::NODE_HAS_DIRTY_DESCENDANTS_FOR_SERVO;
 use gecko_bindings::structs::NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE;
+use gecko_bindings::sugar::ownership::HasArcFFI;
 use parking_lot::RwLock;
 use parser::ParserContextExtraData;
 use properties::{ComputedValues, parse_style_attribute};
@@ -504,6 +506,26 @@ impl<'le> TElement for GeckoElement<'le> {
         let node_flags = selector_flags_to_node_flags(flags);
         (self.flags() & node_flags) == node_flags
     }
+
+    fn update_animations(&self, pseudo: Option<&PseudoElement>) {
+        let atom_ptr = PseudoElement::ns_atom_or_null_from_opt(pseudo);
+
+        let computed_data = self.borrow_data().unwrap();
+        let computed_values = computed_data.styles().primary.values();
+
+        let parent_element = self.parent_element();
+        let parent_data = parent_element.as_ref().and_then(|e| e.borrow_data());
+        let parent_values = parent_data.as_ref().map(|d| d.styles().primary.values());
+        let parent_values_opt = parent_values.map(|v|
+            *HasArcFFI::arc_as_borrowed(v)
+        );
+
+        unsafe {
+            Gecko_UpdateAnimations(self.0, atom_ptr,
+                                   HasArcFFI::arc_as_borrowed(&computed_values),
+                                   parent_values_opt);
+        }
+    }
 }
 
 impl<'le> PartialEq for GeckoElement<'le> {

components/style/gecko_bindings/bindings.rs

@@ -541,6 +541,14 @@ extern "C" {
                                            RawGeckoStyleAnimationListBorrowed)
      -> bool;
 }
+extern "C" {
+    pub fn Gecko_UpdateAnimations(aElement: RawGeckoElementBorrowed,
+                                  aPseudoTagOrNull: *mut nsIAtom,
+                                  aComputedValues:
+                                      ServoComputedValuesBorrowed,
+                                  aParentComputedValues:
+                                      ServoComputedValuesBorrowedOrNull);
+}
 extern "C" {
     pub fn Gecko_Atomize(aString: *const ::std::os::raw::c_char, aLength: u32)
      -> *mut nsIAtom;

components/style/matching.rs

@@ -556,7 +556,7 @@ trait PrivateMatchMethods: TElement {
     /// Computes values and damage for the primary or pseudo style of an element,
     /// setting them on the ElementData.
     fn cascade_primary_or_pseudo<'a>(&self,
-                                     context: &StyleContext<Self>,
+                                     context: &mut StyleContext<Self>,
                                      data: &mut ElementData,
                                      pseudo: Option<&PseudoElement>,
                                      possibly_expired_animations: &mut Vec<PropertyAnimation>,
@@ -575,7 +575,7 @@ trait PrivateMatchMethods: TElement {
 
         // Handle animations.
         if booleans.animate {
-            self.process_animations(&context,
+            self.process_animations(context,
                                     &mut old_values,
                                     &mut new_values,
                                     pseudo,
@@ -597,16 +597,40 @@ trait PrivateMatchMethods: TElement {
 
     #[cfg(feature = "gecko")]
     fn process_animations(&self,
-                          _context: &StyleContext<Self>,
-                          _old_values: &mut Option<Arc<ComputedValues>>,
-                          _new_values: &mut Arc<ComputedValues>,
-                          _pseudo: Option<&PseudoElement>,
+                          context: &mut StyleContext<Self>,
+                          old_values: &mut Option<Arc<ComputedValues>>,
+                          new_values: &mut Arc<ComputedValues>,
+                          pseudo: Option<&PseudoElement>,
                           _possibly_expired_animations: &mut Vec<PropertyAnimation>) {
+        let ref new_box_style = new_values.get_box();
+        let has_new_animation_style = new_box_style.animation_name_count() >= 1 &&
+                                      new_box_style.animation_name_at(0).0.len() != 0;
+        let needs_update_animations =
+            old_values.as_ref().map_or(has_new_animation_style, |ref old| {
+                let ref old_box_style = old.get_box();
+                let old_display_style = old_box_style.clone_display();
+                let new_display_style = new_box_style.clone_display();
+                // FIXME: If we know that the element has no running CSS animations,
+                // we can also skip the case with checking no_animations.
+                //
+                // FIXME: Bug 1344581: We still need to compare keyframe rules.
+                !old_box_style.animations_equals(&new_box_style) ||
+                 (old_display_style == display::T::none &&
+                  new_display_style != display::T::none &&
+                  has_new_animation_style) ||
+                 (old_display_style != display::T::none &&
+                  new_display_style == display::T::none)
+            });
+        if needs_update_animations {
+            let task = SequentialTask::update_animations(self.as_node().as_element().unwrap(),
+                                                         pseudo.cloned());
+            context.thread_local.tasks.push(task);
+        }
     }
 
     #[cfg(feature = "servo")]
     fn process_animations(&self,
-                          context: &StyleContext<Self>,
+                          context: &mut StyleContext<Self>,
                           old_values: &mut Option<Arc<ComputedValues>>,
                           new_values: &mut Arc<ComputedValues>,
                           _pseudo: Option<&PseudoElement>,
@@ -1033,7 +1057,7 @@ pub trait MatchMethods : TElement {
     /// Run the CSS cascade and compute values for the element, potentially
     /// starting any new transitions or animations.
     fn cascade_element(&self,
-                       context: &StyleContext<Self>,
+                       context: &mut StyleContext<Self>,
                        mut data: &mut AtomicRefMut<ElementData>,
                        primary_is_shareable: bool)
     {