Cleanup: Do not pass a non-const ref in RequestDesktopNotificationPermission.

chrome/browser/chrome_content_browser_client.cc

 // 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.
 
 #include "chrome/browser/chrome_content_browser_client.h"
 
 #include <set>
 #include <utility>
 #include <vector>
 
@@ skipping 2011 matching lines @@
       render_process_id, render_view_id);
 }
 
 content::MediaObserver* ChromeContentBrowserClient::GetMediaObserver() {
   return MediaCaptureDevicesDispatcher::GetInstance();
 }
 
 void ChromeContentBrowserClient::RequestDesktopNotificationPermission(
     const GURL& source_origin,
     content::RenderFrameHost* render_frame_host,
-    base::Closure& callback) {
+    const base::Closure& callback) {
 #if defined(ENABLE_NOTIFICATIONS)
   // Skip showing the infobar if the request comes from an extension, and that
   // extension has the 'notify' permission. (If the extension does not have the
   // permission, the user will still be prompted.)
   Profile* profile = Profile::FromBrowserContext(
       render_frame_host->GetSiteInstance()->GetBrowserContext());
   InfoMap* extension_info_map =
       extensions::ExtensionSystem::Get(profile)->info_map();
   DesktopNotificationService* notification_service =
       DesktopNotificationServiceFactory::GetForProfile(profile);
@@ skipping 709 matching lines @@
       switches::kDisableWebRtcEncryption,
     };
     to_command_line->CopySwitchesFrom(from_command_line,
                                       kWebRtcDevSwitchNames,
                                       arraysize(kWebRtcDevSwitchNames));
   }
 }
 #endif  // defined(ENABLE_WEBRTC)
 
 }  // namespace chrome