Add support for reading .gypi files.

tools/gn/input_conversion.h

 // Copyright (c) 2013 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 TOOLS_GN_INPUT_CONVERSION_H_
 #define TOOLS_GN_INPUT_CONVERSION_H_
 
 #include <string>
 
 class Err;
 class ParseNode;
+class Settings;
 class Value;
 
 extern const char kInputConversion_Help[];
 
 // Converts the given input string (is read from a file or output from a
 // script) to a Value. Conversions as specified in the input_conversion string
 // will be performed. The given origin will be used for constructing the
 // resulting Value.
 //
 // If the conversion string is invalid, the error will be set and an empty
 // value will be returned.
-Value ConvertInputToValue(const std::string& input,
+Value ConvertInputToValue(const Settings* settings,
+                          const std::string& input,
                           const ParseNode* origin,
                           const Value& input_conversion_value,
                           Err* err);
 
 #endif  // TOOLS_GN_INPUT_CONVERSION_H_