[DevTools] Migrate inspector-protocol/emulation tests to new harness

third_party/WebKit/LayoutTests/inspector-protocol/emulation/device-emulation-980-2x.js

+(async function(testRunner) {
+  let {page, session, dp} = await testRunner.startBlank('Tests that device emulation affects media rules, viewport meta tag, body dimensions and window.screen.');
+
+  var DeviceEmulator = await testRunner.loadScript('../resources/device-emulator.js');
+  var deviceEmulator = new DeviceEmulator(testRunner, session);
+  await deviceEmulator.emulate(1200, 1000, 2);
+
+  var viewport = 'w=980';
+  testRunner.log(`Loading page with viewport=${viewport}`);
+  await session.navigate('../resources/device-emulation.html?' + viewport);
+
+  testRunner.log(await session.evaluate(`dumpMetrics(true)`));
+  testRunner.completeTest();
+})