GN: fix a DCHECK() when generating Visual Studio solution files

tools/gn/visual_studio_writer.cc

 // 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.
 
 #include "tools/gn/visual_studio_writer.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 #include <string>
@@ skipping 588 matching lines @@
 void VisualStudioWriter::WriteSolutionFileContents(
     std::ostream& out,
     const base::FilePath& solution_dir_path) {
   out << "Microsoft Visual Studio Solution File, Format Version 12.00"
       << std::endl;
   out << "# " << version_string_ << std::endl;
 
   SourceDir solution_dir(FilePathToUTF8(solution_dir_path));
   for (const SolutionEntry* folder : folders_) {
     out << "Project(\"" << kGuidTypeFolder << "\") = \"(" << folder->name
-        << ")\", \"" << RebasePath(folder->path, solution_dir, "/") << "\", \""
+        << ")\", \"" << RebasePath(folder->path, solution_dir) << "\", \""
         << folder->guid << "\"" << std::endl;
     out << "EndProject" << std::endl;
   }
 
   for (const SolutionEntry* project : projects_) {
     out << "Project(\"" << kGuidTypeProject << "\") = \"" << project->name
-        << "\", \"" << RebasePath(project->path, solution_dir, "/") << "\", \""
+        << "\", \"" << RebasePath(project->path, solution_dir) << "\", \""
         << project->guid << "\"" << std::endl;
     out << "EndProject" << std::endl;
   }
 
   out << "Global" << std::endl;
 
   out << "\tGlobalSection(SolutionConfigurationPlatforms) = preSolution"
       << std::endl;
   const std::string config_mode_prefix =
       std::string(is_debug_config_ ? "Debug" : "Release") + '|';
@@ skipping 117 matching lines @@
                            base::CompareCase::SENSITIVE)) {
         folder->parent_folder = parents.back();
         break;
       } else {
         parents.pop_back();
       }
     }
     parents.push_back(folder);
   }
 }