Restore dir reader fallback header for OSX support

src/base/files/dir_reader_fallback.h

@@ -0,0 +1,35 @@
+// Copyright (c) 2012 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.
+
+#ifndef BASE_FILES_DIR_READER_FALLBACK_H_
+#define BASE_FILES_DIR_READER_FALLBACK_H_
+
+namespace base {
+
+class DirReaderFallback {
+ public:
+  // Open a directory. If |IsValid| is true, then |Next| can be called to start
+  // the iteration at the beginning of the directory.
+  explicit DirReaderFallback(const char* directory_path) {}
+
+  // After construction, IsValid returns true iff the directory was
+  // successfully opened.
+  bool IsValid() const { return false; }
+
+  // Move to the next entry returning false if the iteration is complete.
+  bool Next() { return false; }
+
+  // Return the name of the current directory entry.
+  const char* name() { return nullptr;}
+
+  // Return the file descriptor which is being used.
+  int fd() const { return -1; }
+
+  // Returns true if this is a no-op fallback class (for testing).
+  static bool IsFallback() { return true; }
+};
+
+}  // namespace base
+
+#endif  // BASE_FILES_DIR_READER_FALLBACK_H_