[ServiceWorker] Update formatting for tests.

LayoutTests/http/tests/serviceworker/resources/fetch-access-control-worker.js

 var port = undefined;
 var isTestTargetFetch = false;
 
 self.onmessage = function(e) {
   var message = e.data;
   if ('port' in message) {
     port = message.port;
   } else if (message.msg === 'START TEST CASE') {
     isTestTargetFetch = true;
     port.postMessage({msg: 'READY'});
@@ skipping 19 matching lines @@
   if (params['method']) {
     init['method'] = params['method'];
   }
   if (params['mode']) {
     init['mode'] = params['mode'];
   }
   if (params['credentials']) {
     init['credentials'] = params['credentials'];
   }
   if (params['headers'] === 'CUSTOM') {
-    init['headers'] = {"X-ServiceWorker-Test": "test"};
+    init['headers'] = {'X-ServiceWorker-Test': 'test'};
   } else if (params['headers'] === '{}') {
     init['headers'] = {};
   }
   return init;
 }
 
 function headersToArray(headers) {
   var ret = [];
   for (var header of headers) {
     ret.push(header);
@@ skipping 52 matching lines @@
                 port.postMessage({fetchResult: 'rejected'});
                 reject();
               });
         } catch (e) {
           // Send the result to fetch-access-control.html.
           port.postMessage({fetchResult: 'error'});
           reject();
         }
       }));
   });