Fix the case where the browser livelocks if we cannot open a file.

base/file_util.h

Index: base/file_util.h
diff --git a/base/file_util.h b/base/file_util.h
index 543a86c7779d608c39aabe8cc6d9ddbcff7d283d..094b54bd3bb1dc1ba70ec7d72c5d74e1b3206abb 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -161,6 +161,9 @@ bool CopyDirectory(const std::wstring& from_path, const std::wstring& to_path,
 // false otherwise.
 bool PathExists(const FilePath& path);
 
+// Returns true if the given path is readable by the user, false otherwise.
+bool PathIsReadable(const FilePath& path);
+
 // Returns true if the given path is writable by the user, false otherwise.
 bool PathIsWritable(const FilePath& path);