[inspector_protocol] Allow custom json parser.

lib/Forward_h.template

 // 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 {{"_".join(config.protocol.namespace)}}_Forward_h
 #define {{"_".join(config.protocol.namespace)}}_Forward_h
 
 {% if config.lib.export_header %}
 #include {{format_include(config.lib.export_header)}}
 {% endif %}
-#include {{format_include(config.lib.platform_header)}}
 #include {{format_include(config.lib.string_header)}}
 
 #include <vector>
 
 {% for namespace in config.protocol.namespace %}
 namespace {{namespace}} {
 {% endfor %}
 
 template<typename T> class Array;
 class DictionaryValue;
 class DispatchResponse;
 class ErrorSupport;
 class FundamentalValue;
 class ListValue;
 template<typename T> class Maybe;
 class Object;
 using Response = DispatchResponse;
 class SerializedValue;
 class StringValue;
 class UberDispatcher;
 class Value;
 
 {% for namespace in config.protocol.namespace %}
 } // namespace {{namespace}}
 {% endfor %}
 
 #endif // !defined({{"_".join(config.protocol.namespace)}}_Forward_h)