Add ElementAnimationState and PossibleElementAnimationState

This refactor is preparation for implementing a specification
compliant transitions and animations processing model.

These data structures hold all the animation information about a single
node. Since adding, updating, and modifying animations for a single node
are all interdependent, it makes sense to start encapsulating animation
data and functionality into a single data structure. This also opens up
the possibility for easier concurrency in the future by more easily
allowing per-node mutexes.

components/style/context.rs

@@ -5,7 +5,7 @@
 //! The context within which style is calculated.
 
 #[cfg(feature = "servo")]
-use crate::animation::Animation;
+use crate::animation::ElementAnimationState;
 use crate::bloom::StyleBloom;
 use crate::data::{EagerPseudoStyles, ElementData};
 #[cfg(feature = "servo")]
@@ -29,8 +29,6 @@ use crate::timer::Timer;
 use crate::traversal::DomTraversal;
 use crate::traversal_flags::TraversalFlags;
 use app_units::Au;
-#[cfg(feature = "servo")]
-use crossbeam_channel::Sender;
 use euclid::default::Size2D;
 use euclid::Scale;
 use fxhash::FxHashMap;
@@ -43,8 +41,6 @@ use servo_arc::Arc;
 use servo_atoms::Atom;
 use std::fmt;
 use std::ops;
-#[cfg(feature = "servo")]
-use std::sync::Mutex;
 use style_traits::CSSPixel;
 use style_traits::DevicePixel;
 #[cfg(feature = "servo")]
@@ -54,22 +50,6 @@ use uluru::{Entry, LRUCache};
 
 pub use selectors::matching::QuirksMode;
 
-/// This structure is used to create a local style context from a shared one.
-#[cfg(feature = "servo")]
-pub struct ThreadLocalStyleContextCreationInfo {
-    new_animations_sender: Sender<Animation>,
-}
-
-#[cfg(feature = "servo")]
-impl ThreadLocalStyleContextCreationInfo {
-    /// Trivially constructs a `ThreadLocalStyleContextCreationInfo`.
-    pub fn new(animations_sender: Sender<Animation>) -> Self {
-        ThreadLocalStyleContextCreationInfo {
-            new_animations_sender: animations_sender,
-        }
-    }
-}
-
 /// A global options structure for the style system. We use this instead of
 /// opts to abstract across Gecko and Servo.
 #[derive(Clone)]
@@ -186,25 +166,13 @@ pub struct SharedStyleContext<'a> {
     /// A map with our snapshots in order to handle restyle hints.
     pub snapshot_map: &'a SnapshotMap,
 
-    /// The animations that are currently running.
+    /// The state of all animations for our styled elements.
     #[cfg(feature = "servo")]
-    pub running_animations: Arc<RwLock<FxHashMap<OpaqueNode, Vec<Animation>>>>,
-
-    /// The list of animations that have expired since the last style recalculation.
-    #[cfg(feature = "servo")]
-    pub expired_animations: Arc<RwLock<FxHashMap<OpaqueNode, Vec<Animation>>>>,
-
-    /// The list of animations that have expired since the last style recalculation.
-    #[cfg(feature = "servo")]
-    pub cancelled_animations: Arc<RwLock<FxHashMap<OpaqueNode, Vec<Animation>>>>,
+    pub animation_states: Arc<RwLock<FxHashMap<OpaqueNode, ElementAnimationState>>>,
 
     /// Paint worklets
     #[cfg(feature = "servo")]
     pub registered_speculative_painters: &'a dyn RegisteredSpeculativePainters,
-
-    /// Data needed to create the thread-local style context from the shared one.
-    #[cfg(feature = "servo")]
-    pub local_context_creation_data: Mutex<ThreadLocalStyleContextCreationInfo>,
 }
 
 impl<'a> SharedStyleContext<'a> {
@@ -741,10 +709,6 @@ pub struct ThreadLocalStyleContext<E: TElement> {
     pub rule_cache: RuleCache,
     /// The bloom filter used to fast-reject selector-matching.
     pub bloom_filter: StyleBloom<E>,
-    /// A channel on which new animations that have been triggered by style
-    /// recalculation can be sent.
-    #[cfg(feature = "servo")]
-    pub new_animations_sender: Sender<Animation>,
     /// A set of tasks to be run (on the parent thread) in sequential mode after
     /// the rest of the styling is complete. This is useful for
     /// infrequently-needed non-threadsafe operations.
@@ -778,12 +742,6 @@ impl<E: TElement> ThreadLocalStyleContext<E> {
             sharing_cache: StyleSharingCache::new(),
             rule_cache: RuleCache::new(),
             bloom_filter: StyleBloom::new(),
-            new_animations_sender: shared
-                .local_context_creation_data
-                .lock()
-                .unwrap()
-                .new_animations_sender
-                .clone(),
             tasks: SequentialTaskList(Vec::new()),
             selector_flags: SelectorFlagsMap::new(),
             statistics: PerThreadTraversalStatistics::default(),