Convert //extensions/browser from scoped_ptr to std::unique_ptr

extensions/browser/extension_message_filter.h

Index: extensions/browser/extension_message_filter.h
diff --git a/extensions/browser/extension_message_filter.h b/extensions/browser/extension_message_filter.h
index 65900d13848babca0bd4772f0787af27e4155829..d804d8f01ae0f83a35c02ad35cf6212635b41f31 100644
--- a/extensions/browser/extension_message_filter.h
+++ b/extensions/browser/extension_message_filter.h
@@ -86,7 +86,8 @@ class ExtensionMessageFilter : public content::BrowserMessageFilter {
 
   const int render_process_id_;
 
-  scoped_ptr<KeyedServiceShutdownNotifier::Subscription> shutdown_notifier_;
+  std::unique_ptr<KeyedServiceShutdownNotifier::Subscription>
+      shutdown_notifier_;
 
   // Only access from the UI thread.
   content::BrowserContext* browser_context_;