[iOS][gn] Port blink_html_tokenizer to build with gn.

ios/third_party/blink/blink_html_tokenizer.gyp

 # Copyright 2014 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: //ios/third_party/blink:html_tokenizer
       'target_name': 'blink_html_tokenizer',
       'type': 'static_library',
       'dependencies': [
         '../../../base/base.gyp:base',
       ],
       'include_dirs': [
         '../../..',
       ],
       'sources': [
         'src/html_character_provider.h',
         'src/html_input_stream_preprocessor.h',
         'src/html_markup_tokenizer_inlines.h',
         'src/html_token.h',
         'src/html_token.mm',
         'src/html_tokenizer.h',
         'src/html_tokenizer.mm',
         'src/html_tokenizer_adapter.h',
       ],
     },
   ],
 }