LibWeb: Track an Animation's play/pause task state

This only tracks whether the relevant steps should be executed at some
future (but very soon) time. This time will eventually be whenever the
"update animations and send events" procedure is invoked.

Userland/Libraries/LibWeb/Animations/Animation.cpp

@@ -54,10 +54,14 @@ void Animation::set_effect(JS::GCPtr<AnimationEffect> new_effect)
     if (new_effect == old_effect)
         return;
 
-    // FIXME: 3. If animation has a pending pause task, reschedule that task to run as soon as animation is ready.
+    // 3. If animation has a pending pause task, reschedule that task to run as soon as animation is ready.
+    if (m_pending_pause_task == TaskState::Pending)
+        m_pending_pause_task = TaskState::RunAsSoonAsReady;
 
-    // FIXME: 4. If animation has a pending play task, reschedule that task to run as soon as animation is ready to play
-    //           new effect.
+    // 4. If animation has a pending play task, reschedule that task to run as soon as animation is ready to play ne
+    //    effect.
+    if (m_pending_play_task == TaskState::Pending)
+        m_pending_play_task = TaskState::RunAsSoonAsReady;
 
     // 5. If new effect is not null and if new effect is the associated effect of another animation, previous animation,
     //    run the procedure to set the associated effect of an animation (this procedure) on previous animation passing
@@ -143,8 +147,13 @@ void Animation::set_start_time(Optional<double> const& new_start_time)
         m_hold_time = previous_current_time;
     }
 
-    // FIXME: 7. If animation has a pending play task or a pending pause task, cancel that task and resolve animation’s
-    //           current ready promise with animation.
+    // 7. If animation has a pending play task or a pending pause task, cancel that task and resolve animation’s current
+    //    ready promise with animation.
+    if (m_pending_play_task == TaskState::Pending || m_pending_pause_task == TaskState::Pending) {
+        m_pending_play_task = TaskState::None;
+        m_pending_pause_task = TaskState::None;
+        WebIDL::resolve_promise(realm(), current_ready_promise(), this);
+    }
 
     // FIXME: 8. Run the procedure to update an animation’s finished state for animation with the did seek flag set to
     //           true, and the synchronously notify flag set to false.

Userland/Libraries/LibWeb/Animations/Animation.h

@@ -55,6 +55,12 @@ protected:
     virtual void visit_edges(Cell::Visitor&) override;
 
 private:
+    enum class TaskState {
+        None,
+        Pending,
+        RunAsSoonAsReady,
+    };
+
     void apply_any_pending_playback_rate();
 
     JS::NonnullGCPtr<WebIDL::Promise> current_ready_promise() const;
@@ -90,6 +96,12 @@ private:
 
     // https://www.w3.org/TR/web-animations-1/#current-finished-promise
     mutable JS::GCPtr<WebIDL::Promise> m_current_finished_promise;
+
+    // https://www.w3.org/TR/web-animations-1/#pending-play-task
+    TaskState m_pending_play_task { TaskState::None };
+
+    // https://www.w3.org/TR/web-animations-1/#pending-pause-task
+    TaskState m_pending_pause_task { TaskState::None };
 };
 
 }