GN: Move towards only using / on Windows

tools/gn/ninja_helper.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/ninja_helper.h"
 
 #include "base/logging.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/target.h"
 
 namespace {
 
 const char kLibDirWithSlash[] = "lib/";
 const char kObjectDirNoSlash[] = "obj";
 
 }  // namespace
 
 NinjaHelper::NinjaHelper(const BuildSettings* build_settings)
     : build_settings_(build_settings) {
   build_to_src_no_last_slash_ = build_settings->build_to_source_dir_string();
   if (!build_to_src_no_last_slash_.empty() &&
       build_to_src_no_last_slash_[build_to_src_no_last_slash_.size() - 1] ==
           '/')
     build_to_src_no_last_slash_.resize(build_to_src_no_last_slash_.size() - 1);
 
   build_to_src_system_no_last_slash_ = build_to_src_no_last_slash_;
-  ConvertPathToSystem(&build_to_src_system_no_last_slash_);
 }
 
 NinjaHelper::~NinjaHelper() {
 }
 
 std::string NinjaHelper::GetTopleveOutputDir() const {
   return kObjectDirNoSlash;
 }
 
 std::string NinjaHelper::GetTargetOutputDir(const Target* target) const {
@@ skipping 187 matching lines @@
   if (settings->IsWin()) {
     if (type == SOURCE_RC)
       return prefix + "rc";
   } else {
     if (type == SOURCE_S)
       return prefix + "cc";  // Assembly files just get compiled by CC.
   }
 
   return std::string();
 }