[Extensions] Make Event::restrict_to_browser_context const.

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

Index: chrome/browser/extensions/api/input_ime/input_ime_api_chromeos.cc
diff --git a/chrome/browser/extensions/api/input_ime/input_ime_api_chromeos.cc b/chrome/browser/extensions/api/input_ime/input_ime_api_chromeos.cc
index 53b5f0fcf3abbe45f5198f7d3b27cbac8533e46c..2eb232923289c20db73ec0642d9ae9d3e3d638bb 100644
--- a/chrome/browser/extensions/api/input_ime/input_ime_api_chromeos.cc
+++ b/chrome/browser/extensions/api/input_ime/input_ime_api_chromeos.cc
@@ -217,9 +217,8 @@ class ImeObserverChromeOS : public ui::ImeObserver {
       }
     }
 
-    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));
   }