Make the TestServer use an absolute document root path.

chrome/browser/extensions/extension_apitest.cc

 // Copyright (c) 2012 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 "base/string_util.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/extensions/api/test/test_api.h"
 #include "chrome/browser/extensions/extension_service.h"
@@ skipping 281 matching lines @@
                            test_server()->host_port_pair().port());
 
   return true;
 }
 
 bool ExtensionApiTest::StartWebSocketServer(
     const base::FilePath& root_directory) {
   websocket_server_.reset(new net::TestServer(
       net::TestServer::TYPE_WS,
       net::TestServer::kLocalhost,
-      root_directory));
+      net::TestServer::GetSourceRelativePath(root_directory)));
 
   if (!websocket_server_->Start())
     return false;
 
   test_config_->SetInteger(kTestWebSocketPort,
                            websocket_server_->host_port_pair().port());
 
   return true;
 }
 
 void ExtensionApiTest::SetUpCommandLine(CommandLine* command_line) {
   ExtensionBrowserTest::SetUpCommandLine(command_line);
   test_data_dir_ = test_data_dir_.AppendASCII("api_test");
 }