Add a Dns preresolve interface in //content

chrome/browser/chromeos/login/auth/auth_prewarmer.cc

 // Copyright 2014 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 "chrome/browser/chromeos/login/auth/auth_prewarmer.h"
 
 #include <stddef.h>
 
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/login/helper.h"
@@ skipping 79 matching lines @@
       NOTREACHED();
   }
 }
 
 void AuthPrewarmer::DoPrewarm() {
   const int kConnectionsNeeded = 1;
   const GURL& url = GaiaUrls::GetInstance()->service_login_url();
   content::BrowserThread::PostTask(
       content::BrowserThread::IO, FROM_HERE,
       base::Bind(&content::PreconnectUrl,
-                 base::RetainedRef(GetRequestContext()), url, url,
-                 kConnectionsNeeded, true,
+                 ProfileHelper::GetSigninProfile()->GetResourceContext(), url,

[eroman, 2016/05/31 20:45:27]

why this change? (i.e. as opposed to just removing base::RetainedRef())

(should be the same currently, but barring more information why not re-use the
existing abstraction of this class, GetRequestContext() ?)

[Charlie Harrison, 2016/05/31 21:14:47]

Talked to mmenke@ about it and he said ResourceContext is the better abstraction
than URLRequestContextGetter for this. Also, I have some plans to use the
ResourceContext to delegate back up to the ProfileIOData in //chrome RDHD, which
seems to be the common pattern there. 

+                 url, kConnectionsNeeded, true,
                  net::HttpRequestInfo::EARLY_LOAD_MOTIVATED));
   if (!completion_callback_.is_null()) {
     content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
                                      completion_callback_);
   }
 }
 
 bool AuthPrewarmer::IsNetworkConnected() const {
   NetworkStateHandler* nsh = NetworkHandler::Get()->network_state_handler();
   return (nsh->ConnectedNetworkByType(NetworkTypePattern::Default()) != NULL);
 }
 
 net::URLRequestContextGetter* AuthPrewarmer::GetRequestContext() const {
   return login::GetSigninContext();
 }
 
 }  // namespace chromeos