Add remoting and PPAPI tests to GN build

ppapi/ppapi_host.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.
 
 {
    'targets': [
     {
-      # GN version: //ppapi:ppapi_host
+      # GN version: //ppapi/host
       'target_name': 'ppapi_host',
       'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../ipc/ipc.gyp:ipc',
         '../media/media.gyp:shared_memory_support',
         '../ui/surface/surface.gyp:surface',
         '../url/url.gyp:url_lib',
         'ppapi.gyp:ppapi_c',
         'ppapi_internal.gyp:ppapi_ipc',
@@ skipping 21 matching lines @@
         'host/resource_host.cc',
         'host/resource_host.h',
         'host/resource_message_filter.cc',
         'host/resource_message_filter.h',
         'host/resource_message_handler.cc',
         'host/resource_message_handler.h',
       ],
     },
   ],
 }