Move proto files back into chrome/browser/policy/proto

chrome/browser/policy/proto/cloud/chrome_extension_policy.proto

 // Copyright (c) 2013 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.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package enterprise_management;
 
@@ skipping 23 matching lines @@
 
     // The HTTP GET request sent to |download_url| must include an
     // "Authorization: " HTTP header of the "OAuth" type. Its value is a valid
     // Google Accounts OAuth access token.
     OAUTH = 2;
   }
 
   // The authentication method that the client must use to fetch |download_url|.
   optional AuthMethod download_auth_method = 3 [default = NONE];
 }