LibWeb: Add the Animation IDL object

Userland/Libraries/LibWeb/Animations/Animation.idl

@@ -0,0 +1,42 @@
+#import <Animations/AnimationEffect.idl>
+#import <Animations/AnimationTimeline.idl>
+
+// https://www.w3.org/TR/web-animations-1/#the-animation-interface
+[Exposed=Window]
+interface Animation : EventTarget {
+    constructor(optional AnimationEffect? effect = null,
+                optional AnimationTimeline? timeline);
+             attribute DOMString                id;
+             attribute AnimationEffect?         effect;
+             attribute AnimationTimeline?       timeline;
+             attribute double?                  startTime;
+             attribute double?                  currentTime;
+             attribute double                   playbackRate;
+    readonly attribute AnimationPlayState       playState;
+    readonly attribute AnimationReplaceState    replaceState;
+    // FIXME:
+    // readonly attribute boolean                  pending;
+    readonly attribute Promise<Animation>       ready;
+    readonly attribute Promise<Animation>       finished;
+
+    // FIXME:
+    //       attribute EventHandler             onfinish;
+    //       attribute EventHandler             oncancel;
+    //       attribute EventHandler             onremove;
+
+    // undefined cancel();
+    // undefined finish();
+    // undefined play();
+    // undefined pause();
+    // undefined updatePlaybackRate(double playbackRate);
+    // undefined reverse();
+    // undefined persist();
+    // [CEReactions]
+    // undefined commitStyles();
+};
+
+// https://www.w3.org/TR/web-animations-1/#the-animationplaystate-enumeration
+enum AnimationPlayState { "idle", "running", "paused", "finished" };
+
+// https://www.w3.org/TR/web-animations-1/#the-animationreplacestate-enumeration
+enum AnimationReplaceState { "active", "removed", "persisted" };