websocket-to-TCP proxy: observe value of listening port in right place.

chrome/browser/extensions/extension_web_socket_proxy_private_apitest.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/common/chrome_switches.h"
 
 class ExtensionWebSocketProxyPrivateApiTest : public ExtensionApiTest {
   void SetUpCommandLine(CommandLine* command_line) {
     ExtensionApiTest::SetUpCommandLine(command_line);
     command_line->AppendSwitchASCII(
         switches::kAllowWebSocketProxy, "mknjjldhaihcdajjbihghhiehamnpcak");
   }
 };
 
 IN_PROC_BROWSER_TEST_F(ExtensionWebSocketProxyPrivateApiTest, Pass) {
   // Currently WebSocket-to-TCP proxy is operational only on ChromeOS platform.
 #if defined(OS_CHROMEOS)
   ASSERT_TRUE(StartTestServer());
   ASSERT_TRUE(RunExtensionTest("web_socket_proxy_private")) << message_;
+  // Check if API still works on subsequent calls.
+  ASSERT_TRUE(RunExtensionTest("web_socket_proxy_private")) << message_;
 #endif
 }