Make content::PermissionType an enum class.

content/public/browser/permission_type.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_PERMISSION_TYPE_H_
 #define CONTENT_PUBLIC_BROWSER_PERMISSION_TYPE_H_
 
 namespace content {
 
 // This enum is also used for UMA purposes, so it needs to adhere to
 // the UMA guidelines.
 // Make sure you update histograms.xml if you add new permission types.
 // Never delete or reorder an entry; only add new entries
-// immediately before PERMISSION_NUM
-enum PermissionType {
-  PERMISSION_MIDI_SYSEX = 1,
-  PERMISSION_PUSH_MESSAGING = 2,
-  PERMISSION_NOTIFICATIONS = 3,
-  PERMISSION_GEOLOCATION = 4,
-  PERMISSION_PROTECTED_MEDIA_IDENTIFIER = 5,
+// immediately before PermissionType::NUM
+enum class PermissionType {
+  MIDI_SYSEX = 1,
+  PUSH_MESSAGING = 2,
+  NOTIFICATIONS = 3,
+  GEOLOCATION = 4,
+  PROTECTED_MEDIA_IDENTIFIER = 5,
 
   // Always keep this at the end.
-  PERMISSION_NUM,
+  NUM,
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_PERMISSION_TYPE_H_