GN: Move towards only using / on Windows

tools/gn/filesystem_utils.cc

 // 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.
 
 #include "tools/gn/filesystem_utils.h"
 
 #include <algorithm>
 
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 544 matching lines @@
 
 void ConvertPathToSystem(std::string* path) {
 #if defined(OS_WIN)
   for (size_t i = 0; i < path->size(); i++) {
     if ((*path)[i] == '/')
       (*path)[i] = '\\';
   }
 #endif
 }
 
-std::string PathToSystem(const std::string& path) {
-  std::string ret(path);
-  ConvertPathToSystem(&ret);
-  return ret;
-}
-
 std::string RebaseSourceAbsolutePath(const std::string& input,
                                      const SourceDir& dest_dir) {
   CHECK(input.size() >= 2 && input[0] == '/' && input[1] == '/')
       << "Input to rebase isn't source-absolute: " << input;
   CHECK(dest_dir.is_source_absolute())
       << "Dir to rebase to isn't source-absolute: " << dest_dir.value();
 
   const std::string& dest = dest_dir.value();
 
   // Skip the common prefixes of the source and dest as long as they end in
@@ skipping 149 matching lines @@
   return GetGenDirForSourceDir(target->settings(), target->label().dir());
 }
 
 SourceDir GetCurrentOutputDir(const Scope* scope) {
   return GetOutputDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }
 
 SourceDir GetCurrentGenDir(const Scope* scope) {
   return GetGenDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }