FileTypePolicies class to load types from proto.

chrome/browser/resources/safe_browsing/download_file_types.asciipb

 # Copyright 2016 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.
 
 # See README.md before editing this file.
 #
 # Placeholder for list of file extensions that the download manager
 # knows about.
 # TODO(nparker): Populate this with full list.
 version_id: 1
 sampled_ping_probability: 0.0
 default_file_type {
-  uma_value: 19
+  uma_value: 18
   platform_settings {
     danger_level: ALLOW_ON_USER_GESTURE
     auto_open_hint: DISALLOW_AUTO_OPEN
     ping_setting: SAMPLED_PING
   }
 }
 #
 # File types:
 #
 file_types {
   extension: "exe"
-  uma_value: 777
+  uma_value: 0
   platform_settings {
     danger_level: ALLOW_ON_USER_GESTURE
     auto_open_hint: DISALLOW_AUTO_OPEN
     ping_setting: FULL_PING
   }
 }
 file_types {
   extension: "zip"
-  uma_value: 888
+  uma_value: 7
   is_archive: true
   platform_settings {
     danger_level: NOT_DANGEROUS
     auto_open_hint: ALLOW_AUTO_OPEN
     ping_setting: SAMPLED_PING
   }
 }
 # file_types {...}
 # file_types {...}
 # file_types {...}