Revert of ServiceWorker: throw when close() or terminate() called

LayoutTests/http/tests/serviceworker/resources/fetch-body-stream-worker.js

 self.onmessage = function(e) {
     var message = e.data;
     if ('port' in message) {
         port = message.port;
         doTextTest(port);
     }
 };
 
 function quit(port) {
     port.postMessage('quit');
+    self.close();
 }
 
 function doFetchTwiceTest(port) {
   var p1Out = p2Out = null;
 
   fetch('doctype.html')
   .then(function(response) {
       var p1 = response.body.asText();
       var p2 = response.body.asText();
 
@@ skipping 63 matching lines @@
 
 function doTextTest(port) {
   fetch('doctype.html')
   .then(function(response) {
       response.body.asText()
       .then(function(txt) {
           port.postMessage('Text: ' + txt);
           doJSONTest(port);
       });
   });
-}
+}