Recomposite transform animations when CSS zoom changes

LayoutTests/virtual/threaded/animations/zoom-responsive-transform-animation.html

Index: LayoutTests/virtual/threaded/animations/zoom-responsive-transform-animation.html
diff --git a/LayoutTests/animations/opacity-responsive-neutral-keyframe.html b/LayoutTests/virtual/threaded/animations/zoom-responsive-transform-animation.html
similarity index 68%
copy from LayoutTests/animations/opacity-responsive-neutral-keyframe.html
copy to LayoutTests/virtual/threaded/animations/zoom-responsive-transform-animation.html
index 86f1587cdc0e2b83831b2dd7b39df9a920e444ae..4ff4615c816a3559c8f938bbb5cacb7a6f2a5173 100644
--- a/LayoutTests/animations/opacity-responsive-neutral-keyframe.html
+++ b/LayoutTests/virtual/threaded/animations/zoom-responsive-transform-animation.html
@@ -4,28 +4,22 @@ div {
   position: absolute;
   width: 100px;
   height: 100px;
-}
-#target {
-  background: red;
-  opacity: 1;
+  background: black;
   animation: test 1e8s;
 }
-#green {
-  background: green;
-}
 @keyframes test {
-  to { opacity: 0.5; }
+  from {transform: translate(100px, 100px);}
+  to {transform: translate(100px, 100px);}
 }
 </style>
-<div id="green"></div>
-<div id="target"></div>
+<div></div>
 <script>
 if (window.testRunner)
   testRunner.waitUntilDone();
 
 requestAnimationFrame(() => {
   requestAnimationFrame(() => {
-    target.style.opacity = 0;
+    internals.setZoomFactor(2);
     requestAnimationFrame(() => {
       if (window.testRunner)
         testRunner.notifyDone();