[Extensions] Make Event::restrict_to_browser_context const.

chrome/browser/extensions/extension_messages_apitest.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 <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <utility>
 
@@ skipping 68 matching lines @@
     event->SetString("data", data);
     std::unique_ptr<base::ListValue> arguments(new base::ListValue());
     arguments->Append(std::move(event));
     return arguments;
   }
 
   static std::unique_ptr<Event> BuildEvent(
       std::unique_ptr<base::ListValue> event_args,
       Profile* profile,
       GURL event_url) {
-    std::unique_ptr<Event> event(new Event(
-        events::TEST_ON_MESSAGE, "test.onMessage", std::move(event_args)));
-    event->restrict_to_browser_context = profile;
+    auto event =
+        base::MakeUnique<Event>(events::TEST_ON_MESSAGE, "test.onMessage",
+                                std::move(event_args), profile);
     event->event_url = event_url;
     return event;
   }
 
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override {
     DCHECK_EQ(extensions::NOTIFICATION_EXTENSION_HOST_DID_STOP_FIRST_LOAD,
               type);
     EventRouter* event_router =
@@ skipping 1220 matching lines @@
   ASSERT_TRUE(content::ExecuteScriptAndExtractInt(
       background_contents,
       "window.domAutomationController.send(window.messageCount);",
       &message_count));
   EXPECT_EQ(1, message_count);
 }
 
 }  // namespace
 
 };  // namespace extensions