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

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

 self.onmessage = function(e) {
     var message = e.data;
     if ('port' in message) {
         port = message.port;
         doNextFetchTest(port);
     }
 };
 
 var testTargets = [
     'other.html',
     'http://',
     'http://www.example.com/foo',
     'fetch-status.php?status=200',
     'fetch-status.php?status=404'
 ];
 
 function doNextFetchTest(port) {
+
+    function runInfiniteFetchLoop() {
+      fetch('dummy.html')
+        .then(function() { runInfiniteFetchLoop(); });
+    }
+
     if (testTargets.length == 0) {
-        port.postMessage('quit');
-        // Destroying the execution context while fetch is happening should not cause a crash.
-        fetch('dummy.html').then(function() {}).catch(function() {});
-        self.close();
-        return;
+      // Destroying the execution context while fetch is happening
+      // should not cause a crash.
+      runInfiniteFetchLoop();
+
+      port.postMessage('quit');
+      return;
     }
     var target = testTargets.shift();
     fetch(target)
     .then(function(response) {
         port.postMessage('Resolved: ' + target + ' [' + response.status + ']' + response.statusText);
         doNextFetchTest(port);
     }).catch(function(e) {
         port.postMessage('Rejected: ' + target + ' : '+ e.message);
         doNextFetchTest(port);
     });
 };