Animations: Introduce compositor AnimationPlayer and AnimationTimeline.

Source/core/animation/DocumentAnimations.cpp

Index: Source/core/animation/DocumentAnimations.cpp
diff --git a/Source/core/animation/DocumentAnimations.cpp b/Source/core/animation/DocumentAnimations.cpp
index 02fa51dd9fef53be95d2f04f8085f367ffff49fa..e8f290c1f588f32af3d87c701c7afe7f2425099e 100644
--- a/Source/core/animation/DocumentAnimations.cpp
+++ b/Source/core/animation/DocumentAnimations.cpp
@@ -87,6 +87,8 @@ bool DocumentAnimations::needsOutdatedAnimationPlayerUpdate(const Document& docu
 void DocumentAnimations::updateCompositorAnimations(Document& document)
 {
     ASSERT(document.lifecycle().state() == DocumentLifecycle::CompositingClean);
+    document.timeline().updateCompositorPlayerToElementAttachments();
+
     if (document.compositorPendingAnimations().update()) {
         ASSERT(document.view());
         document.view()->scheduleAnimation();