[DevTools] New harness for inspector-protocol layout tests

third_party/WebKit/LayoutTests/inspector-protocol/page/frameScheduledNavigation.js

+(async function() {
+  let {page, session, Protocol} = await InspectorTest.startBlank('');
+
+  Protocol.Page.enable();
+  session.evaluate(`
+    var frame = document.createElement('iframe');
+    document.body.appendChild(frame);
+    frame.src = '${InspectorTest.url('../resources/blank.html')}';
+  `);
+
+  var msg = await Protocol.Page.onceFrameScheduledNavigation();
+  InspectorTest.log('Scheduled navigation with delay ' + msg.params.delay);
+
+  await Protocol.Page.onceFrameStartedLoading();
+  // This event should be received before the scheduled navigation is cleared.
+  InspectorTest.log('Started loading');
+
+  await Protocol.Page.onceFrameClearedScheduledNavigation();
+  InspectorTest.log('Cleared scheduled navigation');
+  InspectorTest.completeTest();
+})();