[iOS][GN] Port ios_net_unittests to build with gn.

ios/net/ios_net.gyp

 # Copyright 2015 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
+      # GN version: //ios/net
       'target_name': 'ios_net',
       'type': 'static_library',
       'include_dirs': [
         '../..',
       ],
       'dependencies': [
         '../../base/base.gyp:base',
         '../../net/net.gyp:net',
       ],
       'sources': [
@@ skipping 32 matching lines @@
         'protocol_handler_util.h',
         'protocol_handler_util.mm',
         'request_tracker.h',
         'request_tracker.mm',
         'url_scheme_util.h',
         'url_scheme_util.mm',
       ],
     },
   ],
 }