Get rid of "default:" clause.

chrome/browser/chromeos/arc/arc_auth_service.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.
 
 #include "chrome/browser/chromeos/arc/arc_auth_service.h"
 
 #include <utility>
 
 #include "ash/common/shelf/shelf_delegate.h"
 #include "ash/common/wm_shell.h"
@@ skipping 1128 matching lines @@
 std::ostream& operator<<(std::ostream& os, const ArcAuthService::State& state) {
   switch (state) {
     case ArcAuthService::State::NOT_INITIALIZED:
       return os << "NOT_INITIALIZED";
     case ArcAuthService::State::STOPPED:
       return os << "STOPPED";
     case ArcAuthService::State::FETCHING_CODE:
       return os << "FETCHING_CODE";
     case ArcAuthService::State::ACTIVE:
       return os << "ACTIVE";
-    default:
-      NOTREACHED();
-      return os;
   }
+
+  // Some compiler reports an error even if all values of an enum-class are
+  // covered indivisually in a switch statement.
+  NOTREACHED();
+  return os;
 }
 
 }  // namespace arc