Begin the first small step towards using FilePath everywhere:

base/path_service_unittest.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/path_service.h"
+
 #include "base/basictypes.h"
 #include "base/file_util.h"
+#include "base/file_path.h"
 #include "base/logging.h"
-#include "base/path_service.h"
 #include "base/platform_test.h"
 #if defined(OS_WIN)
 #include "base/win_util.h"
 #endif
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest/include/gtest/gtest-spi.h"
 
 namespace {
 
 // Returns true if PathService::Get returns true and sets the path parameter
 // to non-empty for the given PathService::DirType enumeration value.
 bool ReturnsValidPath(int dir_type) {
-  std::wstring path;
+  FilePath path;
   bool result = PathService::Get(dir_type, &path);
-  return result && !path.empty() && file_util::PathExists(path);
+  return result && !path.value().empty() && file_util::PathExists(path);
 }
 
 #if defined(OS_WIN)
 // Function to test DIR_LOCAL_APP_DATA_LOW on Windows XP. Make sure it fails.
 bool ReturnsInvalidPath(int dir_type) {
   std::wstring path;
   bool result = PathService::Get(base::DIR_LOCAL_APP_DATA_LOW, &path);
   return !result && path.empty();
 }
 #endif
@@ skipping 19 matching lines @@
       // DIR_LOCAL_APP_DATA_LOW is not supported prior Vista and is expected to
       // fail.
       EXPECT_TRUE(ReturnsInvalidPath(key)) << key;
     } else {
       EXPECT_TRUE(ReturnsValidPath(key)) << key;
     }
   }
 #endif
 }