[DevTools] New harness for inspector-protocol layout tests

third_party/WebKit/LayoutTests/inspector-protocol/animation/animation-seek-past-end.js

+(async function() {
+  let {page, session, Protocol} = await InspectorTest.startHTML(`
+    <div id='node' style='background-color: red; height: 100px; width: 100px'></div>
+  `, '');
+
+  Protocol.Animation.enable();
+  session.evaluate(`
+    node.animate([{ width: '1000px' }, { width: '2000px' }], 1000);
+  `);
+
+  var response = await Protocol.Animation.onceAnimationStarted();
+  InspectorTest.log('Animation started');
+  await Protocol.Animation.seekAnimations({ animations: [ response.params.animation.id ], currentTime: 2000 });
+
+  var rafWidth = await session.evaluateAsync(`
+    (function rafWidth() {
+        var callback;
+        var promise = new Promise((fulfill) => callback = fulfill);
+        if (window.testRunner)
+            testRunner.layoutAndPaintAsyncThen(() => callback(node.offsetWidth));
+        return promise;
+    })()
+  `);
+  InspectorTest.log(rafWidth);
+  InspectorTest.completeTest();
+})();