Remove the default argument from RegKey::ReadValue.

base/registry.h

Index: base/registry.h
diff --git a/base/registry.h b/base/registry.h
index 22ec0be1fff720a90eeb5e056534ee18f19b01cc..7584de019aa79f0c6e38c1e66a5855e05ccf8b3b 100644
--- a/base/registry.h
+++ b/base/registry.h
@@ -7,14 +7,10 @@
 #pragma once
 
 #include <windows.h>
-
 #include <string>
 
 #include "base/basictypes.h"
 
-// TODO(tfarina): Get rid of all the default arguments used in this file.
-// They are not allowed by our style guide.
-
 // Utility class to read, write and manipulate the Windows Registry.
 // Registry vocabulary primer: a "key" is like a folder, in which there
 // are "values", which are <name, data> pairs, with an associated data type.
@@ -56,8 +52,7 @@ class RegKey {
 
   bool ValueExists(const wchar_t* name);
 
-  bool ReadValue(const wchar_t* name, void* data, DWORD* dsize,
-                 DWORD* dtype = NULL);
+  bool ReadValue(const wchar_t* name, void* data, DWORD* dsize, DWORD* dtype);
   bool ReadValue(const wchar_t* name, std::wstring* value);
   bool ReadValueDW(const wchar_t* name, DWORD* value);