[WIP] Support PerformanceResourceTiming for Service Worker Navigation Preload

third_party/WebKit/LayoutTests/external/wpt/service-workers/service-worker/navigation-preload/resources/resource-timing-worker.js

+self.addEventListener('activate', event => {
+    event.waitUntil(self.registration.navigationPreload.enable());
+  });
+
+self.addEventListener('fetch', event => {
+    event.respondWith(
+      event.preloadResponse
+          .then(response => {
+            var headers = response.headers;
+            return response.text().then(text =>
+              new Response(
+                JSON.stringify({
+                  decodedBodySize: headers.get('X-Decoded-Body-Size'),
+                  encodedBodySize: headers.get('X-Encoded-Body-Size'),
+                  timingEntries: performance.getEntriesByName(event.request.url)
+                }),
+                {headers: {'Content-Type': 'text/html'}}));
+          }));
+  });