Fix some leaks and failures under valgrind in JS extensions unit tests.

extensions/renderer/resources/serial_service.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 define('serial_service', [
     'content/public/renderer/service_provider',
     'device/serial/serial.mojom',
     'mojo/public/js/bindings/core',
     'mojo/public/js/bindings/router',
 ], function(serviceProvider, serialMojom, core, routerModule) {
   /**
    * A Javascript client for the serial service and connection Mojo services.
    *
    * This provides a thick client around the Mojo services, exposing a JS-style
    * interface to serial connections and information about serial devices. This
    * converts parameters and result between the Apps serial API types and the
    * Mojo types.
    */
 
-  var service = new serialMojom.SerialServiceProxy(new routerModule.Router(
-      serviceProvider.connectToService(serialMojom.SerialServiceProxy.NAME_)));
+  var unloadEvent = require('unload_event');
+  var serviceRouter = new routerModule.Router(
+      serviceProvider.connectToService(serialMojom.SerialServiceProxy.NAME_));
+  var service = new serialMojom.SerialServiceProxy(serviceRouter);
+  unloadEvent.addListener(function() {
+    serviceRouter.close();
+  });

[not at google - send to devlin, 2014/08/27 19:28:58]

Hm, why does the destruction of |serviceRouter| (via the context being
destroyed) not cause it to automatically close? All of its references should
have gone. I.e. is it not enough to just call the RunGCForTesting method and not
change any code in here?

[Sam McNally, 2014/08/28 07:06:51]

It appears "kFullGarbageCollection" doesn't mean what I thought it meant. The
old version does work as expected if the GC is run enough.

 
   function getDevices() {
     return service.getDevices().then(function(response) {
       return $Array.map(response.devices, function(device) {
         var result = {path: device.path || ''};
         if (device.has_vendor_id)
           result.vendorId = device.vendor_id;
         if (device.has_product_id)
           result.productId = device.product_id;
         if (device.display_name)
@@ skipping 233 matching lines @@
     return Promise.resolve(nextConnectionId_++);
   }
 
   return {
     getDevices: getDevices,
     createConnection: Connection.create,
     getConnection: getConnection,
     getConnections: getConnections,
   };
 });