GN: Move towards only using / on Windows

tools/gn/filesystem_utils.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_FILESYSTEM_UTILS_H_
 #define TOOLS_GN_FILESYSTEM_UTILS_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
@@ skipping 120 matching lines @@
 // This will be the empty string for the root directories ("/" and "//"), and
 // in all other cases, this is guaranteed to end in a slash.
 std::string InvertDir(const SourceDir& dir);
 
 // Collapses "." and sequential "/"s and evaluates "..".
 void NormalizePath(std::string* path);
 
 // Converts slashes to backslashes for Windows. Keeps the string unchanged
 // for other systems.
 void ConvertPathToSystem(std::string* path);
-std::string PathToSystem(const std::string& path);
 
 // Takes a source-absolute path (must begin with "//") and makes it relative
 // to the given directory, which also must be source-absolute.
 std::string RebaseSourceAbsolutePath(const std::string& input,
                                      const SourceDir& dest_dir);
 
 // Returns the given directory with no terminating slash at the end, such that
 // appending a slash and more stuff will produce a valid path.
 //
 // If the directory refers to either the source or system root, we'll append
@@ skipping 19 matching lines @@
 SourceDir GetOutputDirForSourceDir(const Settings* settings,
                                    const SourceDir& source_dir);
 SourceDir GetGenDirForSourceDir(const Settings* settings,
                                 const SourceDir& source_dir);
 SourceDir GetTargetOutputDir(const Target* target);
 SourceDir GetTargetGenDir(const Target* target);
 SourceDir GetCurrentOutputDir(const Scope* scope);
 SourceDir GetCurrentGenDir(const Scope* scope);
 
 #endif  // TOOLS_GN_FILESYSTEM_UTILS_H_