HostResolver is exposed to plugin.

ppapi/ppapi_sources.gypi

 # 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.
 
 {
   'variables': {
     'c_source_files': [
       'c/pp_bool.h',
       'c/pp_completion_callback.h',
       'c/pp_errors.h',
@@ skipping 361 matching lines @@
       'tests/test_flash_fullscreen.cc',
       'tests/test_flash_fullscreen.h',
       'tests/test_flash_message_loop.cc',
       'tests/test_flash_message_loop.h',
       'tests/test_fullscreen.cc',
       'tests/test_fullscreen.h',
       'tests/test_graphics_2d.cc',
       'tests/test_graphics_2d.h',
       'tests/test_graphics_3d.cc',
       'tests/test_graphics_3d.h',
+      'tests/test_host_resolver_private.cc',
+      'tests/test_host_resolver_private.h',
       'tests/test_image_data.cc',
       'tests/test_image_data.h',
       'tests/test_input_event.cc',
       'tests/test_input_event.h',
       'tests/test_memory.cc',
       'tests/test_memory.h',
       'tests/test_net_address_private.cc',
       'tests/test_net_address_private.h',
       'tests/test_paint_aggregator.cc',
       'tests/test_paint_aggregator.h',
@@ skipping 39 matching lines @@
           'c/dev/ppb_transport_dev.h',
         ],
         'cpp_source_files': [
           'cpp/dev/transport_dev.cc',
           'cpp/dev/transport_dev.h',
         ],
       },
     }],
   ],
 }