[Extensions] Make Event::restrict_to_browser_context const.

chrome/browser/extensions/api/history/history_api.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/extensions/api/history/history_api.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 155 matching lines @@
   DispatchEvent(profile_, events::HISTORY_ON_VISIT_REMOVED,
                 api::history::OnVisitRemoved::kEventName, std::move(args));
 }
 
 void HistoryEventRouter::DispatchEvent(
     Profile* profile,
     events::HistogramValue histogram_value,
     const std::string& event_name,
     std::unique_ptr<base::ListValue> event_args) {
   if (profile && EventRouter::Get(profile)) {
-    std::unique_ptr<Event> event(
-        new Event(histogram_value, event_name, std::move(event_args)));
-    event->restrict_to_browser_context = profile;
+    auto event = base::MakeUnique<Event>(histogram_value, event_name,
+                                         std::move(event_args), profile);
     EventRouter::Get(profile)->BroadcastEvent(std::move(event));
   }
 }
 
 HistoryAPI::HistoryAPI(content::BrowserContext* context)
     : browser_context_(context) {
   EventRouter* event_router = EventRouter::Get(browser_context_);
   event_router->RegisterObserver(this, api::history::OnVisited::kEventName);
   event_router->RegisterObserver(this,
                                  api::history::OnVisitRemoved::kEventName);
@@ skipping 255 matching lines @@
   AddRef();               // Balanced in DeleteComplete().
   return RespondLater();  // DeleteComplete() will be called asynchronously.
 }
 
 void HistoryDeleteAllFunction::DeleteComplete() {
   Respond(NoArguments());
   Release();  // Balanced in Run().
 }
 
 }  // namespace extensions