[Extensions] Make Event::restrict_to_browser_context const.

extensions/browser/event_router.h

 // 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.
 
 #ifndef EXTENSIONS_BROWSER_EVENT_ROUTER_H_
 #define EXTENSIONS_BROWSER_EVENT_ROUTER_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 345 matching lines @@
   // correlates 1:1 with |event_name|, in some cases events will generate
   // their own names, but they cannot generate their own identifier.
   events::HistogramValue histogram_value;
 
   // The event to dispatch.
   std::string event_name;
 
   // Arguments to send to the event listener.
   std::unique_ptr<base::ListValue> event_args;
 
   // If non-NULL, then the event will not be sent to other BrowserContexts

[Devlin, 2017/05/24 16:08:19]

nit: s/NULL/null

[lazyboy, 2017/05/24 19:19:33]

Done.

   // unless the extension has permission (e.g. incognito tab update -> normal
   // tab only works if extension is allowed incognito access).
-  content::BrowserContext* restrict_to_browser_context;
+  content::BrowserContext* const restrict_to_browser_context;
 
   // If not empty, the event is only sent to extensions with host permissions
   // for this url.
   GURL event_url;
 
   // Whether a user gesture triggered the event.
   EventRouter::UserGestureState user_gesture;
 
   // Extra information used to filter which events are sent to the listener.
   EventFilteringInfo filter_info;
@@ skipping 42 matching lines @@
   const std::string event_name;
 
   const std::string extension_id;
   const GURL listener_url;
   content::BrowserContext* browser_context;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EVENT_ROUTER_H_