[Extensions] Make Event::restrict_to_browser_context const.

chrome/browser/extensions/api/input_ime/input_ime_api_nonchromeos.cc

 // Copyright 2015 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.
 
 // This file is for non-chromeos (win & linux) functions, such as
 // chrome.input.ime.activate, chrome.input.ime.createWindow and
 // chrome.input.ime.onSelectionChanged.
 // TODO(azurewei): May refactor the code structure by using delegate or
 // redesign the API to remove this platform-specific file in the future.
 
@@ skipping 96 matching lines @@
  private:
   // ImeObserver overrides.
   void DispatchEventToExtension(
       extensions::events::HistogramValue histogram_value,
       const std::string& event_name,
       std::unique_ptr<base::ListValue> args) override {
     if (!IsInputImeEnabled()) {
       return;
     }
 
-    std::unique_ptr<extensions::Event> event(
-        new extensions::Event(histogram_value, event_name, std::move(args)));
-    event->restrict_to_browser_context = profile_;
+    auto event = base::MakeUnique<extensions::Event>(
+        histogram_value, event_name, std::move(args), profile_);
     extensions::EventRouter::Get(profile_)
         ->DispatchEventToExtension(extension_id_, std::move(event));
   }
 
   std::string GetCurrentScreenType() override { return "normal"; }
 
   DISALLOW_COPY_AND_ASSIGN(ImeObserverNonChromeOS);
 };
 
 }  // namespace
@@ skipping 281 matching lines @@
     return RespondNow(Error(kErrorNoActiveEngine));
 
   std::unique_ptr<api::input_ime::HideWindow::Params> params(
       api::input_ime::HideWindow::Params::Create(*args_));
   EXTENSION_FUNCTION_VALIDATE(params.get());
   engine->HideImeWindow(params->window_id);
   return RespondNow(NoArguments());
 }
 
 }  // namespace extensions