[ServiceWorker] Disable the cache revalidation when the page is controlled by the ServiceWorker.

LayoutTests/http/tests/serviceworker/resources/fetch-request-no-freshness-headers-worker.js

+var requests = [];
+
+self.addEventListener('message', function(event) {
+    event.data.port.postMessage({requests: requests});
+  });
+
+self.addEventListener('fetch', function(event) {
+    var url = event.request.url;
+    var headers = [];
+    for (var header of event.request.headers) {
+      headers.push(header);
+    }
+    requests.push({
+      url: url,
+      headers: headers,
+    });
+    event.respondWith(fetch(event.request));
+  });