Service Worker: Add Clients.get(id)

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

+self.onfetch = function(e) {
+  if (e.request.url.indexOf('clients-get-frame.html') >= 0) {
+    // On navigation, the client id should be null.
+    if (e.clientId === null) {
+      e.respondWith(fetch(e.request));
+    } else {
+      e.respondWith(Response.error());
+    }
+    return;
+  }
+  e.respondWith(new Response(e.clientId));
+};
+
+self.onmessage = function(e) {
+  var port = e.data.port;
+  var client_ids = e.data.clientIds;
+  var message = [];
+
+  e.waitUntil(Promise.all(
+      client_ids.map(function(client_id) {
+          return self.clients.get(client_id);
+        }))
+      .then(function(clients) {
+          // No matching client for a given id or a matched client is off-origin
+          // from the service worker.
+          if (clients.length == 1 && clients[0] == undefined) {
+            port.postMessage(clients[0]);
+          } else {
+            clients.forEach(function(client) {
+                if (client instanceof Client) {
+                  message.push([client.visibilityState,
+                                client.focused,
+                                client.url,
+                                client.frameType]);
+                } else {
+                  message.push(client);
+                }
+              });
+            port.postMessage(message);
+          }
+        }));
+};