Begin the first small step towards using FilePath everywhere:

base/file_path.cc

 // Copyright (c) 2008 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 "base/file_path.h"
 
+// These includes are just for the *Hack functions, and should be removed
+// when those functions are removed.
+#include "base/string_piece.h"
+#include "base/sys_string_conversions.h"
+
 #if defined(FILE_PATH_USES_WIN_SEPARATORS)
 const FilePath::CharType FilePath::kSeparators[] = FILE_PATH_LITERAL("\\/");
 #else  // FILE_PATH_USES_WIN_SEPARATORS
 const FilePath::CharType FilePath::kSeparators[] = FILE_PATH_LITERAL("/");
 #endif  // FILE_PATH_USES_WIN_SEPARATORS
 
 const FilePath::CharType FilePath::kCurrentDirectory[] = FILE_PATH_LITERAL(".");
 const FilePath::CharType FilePath::kParentDirectory[] = FILE_PATH_LITERAL("..");
 
 // Returns true if |character| is in kSeparators.
@@ skipping 128 matching lines @@
     return path_.length() > letter + 1 && IsSeparator(path_[letter + 1]);
   }
   // Look for a pair of leading separators.
   return path_.length() > 1 && IsSeparator(path_[0]) && IsSeparator(path_[1]);
 #else  // FILE_PATH_USES_DRIVE_LETTERS
   // Look for a separator in the first position.
   return path_.length() > 0 && IsSeparator(path_[0]);
 #endif  // FILE_PATH_USES_DRIVE_LETTERS
 }
 
+#if defined(OS_POSIX)
+// See file_path.h for a discussion of the encoding of paths on POSIX
+// platforms.  These *Hack() functions are not quite correct, but they're
+// only temporary while we fix the remainder of the code.
+// Remember to remove the #includes at the top when you remove these.
+
+// static
+FilePath FilePath::FromWStringHack(const std::wstring& wstring) {
+  return FilePath(base::SysWideToNativeMB(wstring));
+}
+std::wstring FilePath::ToWStringHack() const {
+  return base::SysNativeMBToWide(path_);
+}
+#elif defined(OS_WIN)
+// static
+FilePath FilePath::FromWStringHack(const std::wstring& wstring) {
+  return FilePath(wstring);
+}
+std::wstring FilePath::ToWStringHack() const {
+  return path_;
+}
+#endif
+
 void FilePath::StripTrailingSeparators() {
   // If there is no drive letter, start will be 1, which will prevent stripping
   // the leading separator if there is only one separator.  If there is a drive
   // letter, start will be set appropriately to prevent stripping the first
   // separator following the drive letter, if a separator immediately follows
   // the drive letter.
   StringType::size_type start = FindDriveLetter() + 2;
 
   StringType::size_type last_stripped = StringType::npos;
   for (StringType::size_type pos = path_.length();
        pos > start && IsSeparator(path_[pos - 1]);
        --pos) {
     // If the string only has two separators and they're at the beginning,
     // don't strip them, unless the string began with more than two separators.
     if (pos != start + 1 || last_stripped == start + 2 ||
         !IsSeparator(path_[start - 1])) {
       path_.resize(pos - 1);
       last_stripped = pos;
     }
   }
 }