Const-ify RefCountedThreadSafe::AddRef and Release.

chrome/common/net/url_request_context_getter.cc

 // Copyright (c) 2009 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.
 
 #include "base/message_loop_proxy.h"
 #include "chrome/common/net/url_request_context_getter.h"
 #include "net/url_request/url_request_context.h"
 
 net::CookieStore* URLRequestContextGetter::GetCookieStore() {
   return GetURLRequestContext()->cookie_store();
 }
 
 URLRequestContextGetter::URLRequestContextGetter() : is_main_(false) {}
 
 URLRequestContextGetter::~URLRequestContextGetter() {}
 
-void URLRequestContextGetter::OnDestruct() {
+void URLRequestContextGetter::OnDestruct() const {
   scoped_refptr<base::MessageLoopProxy> io_message_loop_proxy =
       GetIOMessageLoopProxy();
   DCHECK(io_message_loop_proxy);
   if (io_message_loop_proxy) {
     if (io_message_loop_proxy->BelongsToCurrentThread()) {
       delete this;
     } else {
       io_message_loop_proxy->DeleteSoon(FROM_HERE, this);
     }
   }
   // If no IO message loop proxy was available, we will just leak memory.
   // This is also true if the IO thread is gone.
 }