Extensions: Store disable reasons in Sync

sync/protocol/extension_specifics.proto

 // Copyright (c) 2012 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.
 //
 // Sync protocol datatype extension for extensions.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
@@ skipping 30 matching lines @@
   optional bool remote_install = 7;
 
   // Whether this extension was installed by the custodian of a supervised user.
   optional bool installed_by_custodian = 8;
 
   // Whether this extension has explicit user consent access to all urls.
   // This is a tri-state boolean, so, unlike most fields here, it really *is*
   // optional and may be absent. We need this for the time being because we need
   // to know if a user has not set an explicit preference.
   optional bool all_urls_enabled = 9;
+
+  // Bitmask of the set of reasons why the extension is disabled (see
+  // Extension::DisableReason). Only relevant when enabled == false. Note that
+  // old clients (<M45) won't set this, even when enabled is false.
+  optional int32 disable_reasons = 10;
 }