Add a method for normalizing path separators on Windows.

base/file_path.h

Index: base/file_path.h
diff --git a/base/file_path.h b/base/file_path.h
index 61baf8f5ad9e1a2f087f3b847d62786332c72b4c..0efe1a14407bc63e655415ae916f635ed0d2e589 100644
--- a/base/file_path.h
+++ b/base/file_path.h
@@ -304,6 +304,11 @@ class FilePath {
   void WriteToPickle(Pickle* pickle);
   bool ReadFromPickle(Pickle* pickle, void** iter);
 
+#if defined(FILE_PATH_USES_WIN_SEPARATORS)
+  // Normalize all path separators to backslash.
+  FilePath NormalizeWindowsPathSeparators() const;
+#endif
+
   // Compare two strings in the same way the file system does.
   // Note that these always ignore case, even on file systems that are case-
   // sensitive. If case-sensitive comparison is ever needed, add corresponding