Begin the first small step towards using FilePath everywhere:

base/base_paths_linux.cc

 // Copyright (c) 2006-2008 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/base_paths_linux.h"
 
 #include <unistd.h>
 
+#include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/string_piece.h"
 #include "base/sys_string_conversions.h"
 
 namespace base {
 
 bool PathProviderLinux(int key, std::wstring* result) {
-  std::wstring cur;
+  FilePath path;
   switch (key) {
     case base::FILE_EXE:
     case base::FILE_MODULE: { // TODO(evanm): is this correct?
       char bin_dir[PATH_MAX + 1];
       int bin_dir_size = readlink("/proc/self/exe", bin_dir, PATH_MAX);
       if (bin_dir_size < 0 || bin_dir_size > PATH_MAX) {
         NOTREACHED() << "Unable to resolve /proc/self/exe.";
         return false;
       }
       bin_dir[bin_dir_size] = 0;
       *result = base::SysNativeMBToWide(bin_dir);
       return true;
     }
     case base::DIR_SOURCE_ROOT:
       // On linux, unit tests execute two levels deep from the source root.
       // For example:  chrome/{Debug|Hammer}/net_unittest
-      PathService::Get(base::DIR_EXE, &cur);
-      file_util::UpOneDirectory(&cur);
-      file_util::UpOneDirectory(&cur);
-      *result = cur;
+      if (!PathService::Get(base::DIR_EXE, &path))
+        return false;
+      path = path.Append(FilePath::kParentDirectory)
+                 .Append(FilePath::kParentDirectory);
+      *result = path.ToWStringHack();
       return true;
   }
   return false;
 }
 
 }  // namespace base