Don't allow path traversal paths on the base file helpers

base/file_util.h

Index: base/file_util.h
===================================================================
--- base/file_util.h	(revision 175095)
+++ base/file_util.h	(working copy)
@@ -176,6 +176,7 @@
                                    const FilePath& filename2);
 
 // Read the file at |path| into |contents|, returning true on success.
+// This function fails if the |path| contains path traversal components.

[Nico, 2013/01/08 19:20:03]

I would read this and think "I wonder what a path traversal component is". Does
this mean '..'? If so, can you say '..' instead? If it means '..' and '.', can
you add "(., ..)" to the end of the sentence?

 // |contents| may be NULL, in which case this function is useful for its
 // side effect of priming the disk cache.
 // Useful for unit tests.