Eliminate ash::internal namespace

ash/system/chromeos/power/user_activity_notifier.cc

Index: ash/system/chromeos/power/user_activity_notifier.cc
diff --git a/ash/system/chromeos/power/user_activity_notifier.cc b/ash/system/chromeos/power/user_activity_notifier.cc
index a67f33491e92e6a86dc16baa49f13d92b0eade89..7afd3a8ecffd611ff3494850e3fe52c777bd197f 100644
--- a/ash/system/chromeos/power/user_activity_notifier.cc
+++ b/ash/system/chromeos/power/user_activity_notifier.cc
@@ -12,8 +12,6 @@
 #include "ui/wm/core/user_activity_detector.h"
 
 namespace ash {
-namespace internal {
-
 namespace {
 
 // Minimum number of seconds between notifications.
@@ -64,5 +62,4 @@ void UserActivityNotifier::OnUserActivity(const ui::Event* event) {
   }
 }
 
-}  // namespace internal
 }  // namespace ash