[DevTools] New harness for inspector-protocol layout tests

third_party/WebKit/LayoutTests/inspector-protocol/timeline/timeline-layout.js

+(async function() {
+  let {page, session, Protocol} = await InspectorTest.startHTML(`
+    <style>
+    .my-class {
+        min-width: 100px;
+        background-color: red;
+    }
+    </style>
+    <div id='myDiv'>DIV</div>
+  `, '');
+
+  function performActions() {
+    var div = document.querySelector('#myDiv');
+    div.classList.add('my-class');
+    div.offsetWidth;
+    return Promise.resolve();
+  }
+
+  (await InspectorTest.loadScript('../resources/tracing-test.js'))(session);
+  await session.evaluate(performActions.toString());
+  InspectorTest.invokeAsyncWithTracing('performActions', finish);
+
+  function finish(devtoolsEvents) {
+    var schedRecalc = InspectorTest.findEvent('ScheduleStyleRecalculation', 'I');
+    var recalcBegin = InspectorTest.findEvent('UpdateLayoutTree', 'B');
+    var recalcEnd = InspectorTest.findEvent('UpdateLayoutTree', 'E');
+    InspectorTest.log('UpdateLayoutTree frames match: ' + (schedRecalc.args.data.frame === recalcBegin.args.beginData.frame));
+    InspectorTest.log('UpdateLayoutTree elementCount > 0: ' + (recalcEnd.args.elementCount > 0));
+
+    var invalidate = InspectorTest.findEvent('InvalidateLayout', 'I');
+    var layoutBegin = InspectorTest.findEvent('Layout', 'B');
+    var layoutEnd = InspectorTest.findEvent('Layout', 'E');
+
+    InspectorTest.log('InvalidateLayout frames match: ' + (recalcBegin.args.beginData.frame === invalidate.args.data.frame));
+
+    var beginData = layoutBegin.args.beginData;
+    InspectorTest.log('Layout frames match: ' + (invalidate.args.data.frame === beginData.frame));
+    InspectorTest.log('dirtyObjects > 0: ' + (beginData.dirtyObjects > 0));
+    InspectorTest.log('totalObjects > 0: ' + (beginData.totalObjects > 0));
+
+    var endData = layoutEnd.args.endData;
+    InspectorTest.log('has rootNode id: ' + (endData.rootNode > 0));
+    InspectorTest.log('has root quad: ' + !!endData.root);
+
+    InspectorTest.log('SUCCESS: found all expected events.');
+    InspectorTest.completeTest();
+  }
+})();