Revert 57572 - Remove the default argument from RegKey::Open....

base/registry.h

 // Copyright (c) 2010 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_REGISTRY_H_
 #define BASE_REGISTRY_H_
 #pragma once
 
 #include <windows.h>
 
@@ skipping 11 matching lines @@
  public:
   RegKey();
   RegKey(HKEY rootkey, const wchar_t* subkey, REGSAM access);
   ~RegKey();
 
   bool Create(HKEY rootkey, const wchar_t* subkey, REGSAM access);
 
   bool CreateWithDisposition(HKEY rootkey, const wchar_t* subkey,
                              DWORD* disposition, REGSAM access);
 
-  bool Open(HKEY rootkey, const wchar_t* subkey, REGSAM access);
+  bool Open(HKEY rootkey, const wchar_t* subkey, REGSAM access = KEY_READ);
 
   // Creates a subkey or open it if it already exists.
   bool CreateKey(const wchar_t* name, REGSAM access);
 
   // Opens a subkey
   bool OpenKey(const wchar_t* name, REGSAM access);
 
   void Close();
 
   DWORD ValueCount();
@@ skipping 118 matching lines @@
 
   // Current index of the iteration.
   int index_;
 
   wchar_t name_[MAX_PATH];
 
   DISALLOW_COPY_AND_ASSIGN(RegistryKeyIterator);
 };
 
 #endif  // BASE_REGISTRY_H_