[Extensions] Make Event::restrict_to_browser_context const.

extensions/browser/api/idle/idle_manager.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 "extensions/browser/api/idle/idle_manager.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
@@ skipping 32 matching lines @@
     : context_(context) {
 }
 
 DefaultEventDelegate::~DefaultEventDelegate() {
 }
 
 void DefaultEventDelegate::OnStateChanged(const std::string& extension_id,
                                           ui::IdleState new_state) {
   std::unique_ptr<base::ListValue> args(new base::ListValue());
   args->Append(IdleManager::CreateIdleValue(new_state));
-  std::unique_ptr<Event> event(new Event(events::IDLE_ON_STATE_CHANGED,
-                                         idle::OnStateChanged::kEventName,
-                                         std::move(args)));
-  event->restrict_to_browser_context = context_;
+  auto event = base::MakeUnique<Event>(events::IDLE_ON_STATE_CHANGED,
+                                       idle::OnStateChanged::kEventName,
+                                       std::move(args), context_);
   EventRouter::Get(context_)
       ->DispatchEventToExtension(extension_id, std::move(event));
 }
 
 void DefaultEventDelegate::RegisterObserver(EventRouter::Observer* observer) {
   EventRouter::Get(context_)
       ->RegisterObserver(observer, idle::OnStateChanged::kEventName);
 }
 
 void DefaultEventDelegate::UnregisterObserver(EventRouter::Observer* observer) {
@@ skipping 189 matching lines @@
       event_delegate_->OnStateChanged(it->first, new_state);
     monitor.last_state = new_state;
     listener_count += monitor.listeners;
   }
 
   if (listener_count == 0)
     StopPolling();
 }
 
 }  // namespace extensions