Followup for bug when zipping a folder with non-ascii chars in its name.

third_party/zlib/google/zip.cc

 // Copyright (c) 2012 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 "third_party/zlib/google/zip.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/file_enumerator.h"
 #include "base/logging.h"
@@ skipping 33 matching lines @@
         return false;
       }
     }
   } while (num_bytes > 0);
 
   return true;
 }
 
 bool AddEntryToZip(zipFile zip_file, const base::FilePath& path,
                    const base::FilePath& root_path) {
-  std::string str_path =
-      path.AsUTF8Unsafe().substr(root_path.AsUTF8Unsafe().length() + 1);
+  base::FilePath relative_path;
+  bool result = root_path.AppendRelativePath(path, &relative_path);
+  DCHECK(result);
+  std::string str_path = relative_path.AsUTF8Unsafe();
 #if defined(OS_WIN)
   ReplaceSubstringsAfterOffset(&str_path, 0u, "\\", "/");
 #endif
 
   bool is_directory = base::DirectoryExists(path);
   if (is_directory)
     str_path += "/";
 
   if (ZIP_OK != zipOpenNewFileInZip(
       zip_file, str_path.c_str(),
@@ skipping 132 matching lines @@
   if (ZIP_OK != zipClose(zip_file, NULL)) {
     DLOG(ERROR) << "Error closing zip file for fd " << dest_fd;
     success = false;
   }
 
   return success;
 }
 #endif  // defined(OS_POSIX)
 
 }  // namespace zip