Convert download manager to FilePath.

base/file_util.h

Index: base/file_util.h
===================================================================
--- base/file_util.h	(revision 7599)
+++ base/file_util.h	(working copy)
@@ -77,6 +77,8 @@
 
 // Returns "jpg" for path "C:\pics\jojo.jpg", or an empty string if
 // the file has no extension.
+FilePath::StringType GetFileExtensionFromPath(const FilePath& path);
+// Deprecated temporary compatibility function.
 std::wstring GetFileExtensionFromPath(const std::wstring& path);
 
 // Returns 'jojo' for path "C:\pics\jojo.jpg".
@@ -464,8 +466,8 @@
 // Renames a file using the SHFileOperation API to ensure that the target file
 // gets the correct default security descriptor in the new path.
 bool RenameFileAndResetSecurityDescriptor(
-    const std::wstring& source_file_path,
-    const std::wstring& target_file_path);
+    const FilePath& source_file_path,
+    const FilePath& target_file_path);
 
 }  // namespace file_util