Add Web Animations performance tests

tools/perf/page_sets/tough_animation_cases/resources/web_animations_api_check.js

Index: tools/perf/page_sets/tough_animation_cases/resources/web_animations_api_check.js
diff --git a/tools/perf/page_sets/tough_animation_cases/resources/web_animations_api_check.js b/tools/perf/page_sets/tough_animation_cases/resources/web_animations_api_check.js
new file mode 100644
index 0000000000000000000000000000000000000000..95fa271aefd747644deca5797b47ae2ca241a6ed
--- /dev/null
+++ b/tools/perf/page_sets/tough_animation_cases/resources/web_animations_api_check.js
@@ -0,0 +1,21 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+if (!Element.prototype.animate) {
+  Element.prototype.animate = function() {
+    return {
+      pause: function() {},
+    };
+  };
+  // Generate a dummy animation when Web Animations is not present.
+  // This is to ensure frames are generated so telemetry does not see this as a
+  // test failure and turn the perf tree red.
+  requestAnimationFrame(function() {
+    document.body.style.visibility = 'hidden';
+    document.documentElement.style.transition = '1s';
+    requestAnimationFrame(function() {
+      document.documentElement.style.background = 'red';
+    });
+  });
+  window.measurementReady = true;
+}