Web Animations: Zero time of the document timeline should correspond with navigationStart

LayoutTests/web-animations-api/timeline-time.html

Index: LayoutTests/web-animations-api/timeline-time.html
diff --git a/LayoutTests/web-animations-api/timeline-time.html b/LayoutTests/web-animations-api/timeline-time.html
index 9c86843c31507f4ee5d51e3dd25c028f6b9d0fef..a608400be4b1a80c6c1b3567e65cc99d191dc0a3 100644
--- a/LayoutTests/web-animations-api/timeline-time.html
+++ b/LayoutTests/web-animations-api/timeline-time.html
@@ -43,4 +43,15 @@ test(function() {
     rafTest.done();
   });
 })();
+
+(function() {
+  var timeoutTest = async_test('document.timeline.currentTime time should use the same reference as performance.now()');
+
+  setTimeout(function() {
+    timeoutTest.step(function() {
+      assert_less_than(Math.abs(document.timeline.currentTime - performance.now()), 1000);
+    });
+    timeoutTest.done();
+  }, 0);
+})();
 </script>