[Cronet] Add CookieStoreIOS.

components/cronet/ios/test/test_server.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_CRONET_IOS_TEST_TEST_SERVER_H_
 #define COMPONENTS_CRONET_IOS_TEST_TEST_SERVER_H_
 
 #include <string>
 
 namespace cronet {
 
 class TestServer {
  public:
   static bool Start();
   static void Shutdown();
 
+  // Returns URL which respond with echo of header with |header_name| in
+  // response body.
   static std::string GetEchoHeaderURL(const std::string& header_name);
+  // Returns URL which respond with setting cookie to |cookie_line| and echo it
+  // in response body.
+  static std::string GetSetCookieURL(const std::string& cookie_line);
 };
 
 }  // namespace cronet
 
 #endif  // COMPONENTS_CRONET_IOS_TEST_TEST_SERVER_H_