Apply custom property animation

third_party/WebKit/LayoutTests/animations/custom-properties/unregistered-element-animate.html

Index: third_party/WebKit/LayoutTests/animations/custom-properties/unregistered-element-animate.html
diff --git a/third_party/WebKit/LayoutTests/animations/custom-properties/unregistered-element-animate.html b/third_party/WebKit/LayoutTests/animations/custom-properties/unregistered-element-animate.html
new file mode 100644
index 0000000000000000000000000000000000000000..a75ccf8a74da953d99945cb7b72768c3d097acac
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/animations/custom-properties/unregistered-element-animate.html
@@ -0,0 +1,19 @@
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<style>
+#target {
+  background-color: var(--x);
+}
+</style>
+<div id="target"></div>
+<script>
+test(() => {
+  var animation = target.animate({'--x': ['green', 'lime']}, 1000);
+  animation.currentTime = 250;
+  assert_equals(getComputedStyle(target).getPropertyValue('--x'), 'green');
+  assert_equals(getComputedStyle(target).backgroundColor, 'rgb(0, 128, 0)');
+  animation.currentTime = 750;
+  assert_equals(getComputedStyle(target).getPropertyValue('--x'), 'lime');
+  assert_equals(getComputedStyle(target).backgroundColor, 'rgb(0, 255, 0)');
+}, 'element.animate() animations should apply custom properties');
+</script>