Upstream service worker `client` tests to WPT

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 ||
-      e.request.url.indexOf('clients-get-client-types') >= 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);
-          }
-        }));
-};