Service Worker: Add Clients.get(id)

third_party/WebKit/LayoutTests/http/tests/serviceworker/resources/clients-get-worker.js

+var actual_client_id;
+
+self.onfetch = function(e) {
+    // Get the subresource request from the second iframe.
+    if (e.request.url.indexOf('simple.txt') != -1) {
+      clients.matchAll().then(function(clients) {
+          clients.forEach(function(client) {
+              if (client.frameType == "nested" &&
+                  client.url.indexOf('#2') != -1) {
+                actual_client_id = client.id;
+              }
+            });
+        });
+    }
+};
+
+self.onmessage = function(e) {
+  var port = e.data.port;
+
+  clients.get(actual_client_id).then(function(client) {
+      port.postMessage(client.url);
+    });
+};