Revert 231221 - "Remove enabled/disabled state from extension and app 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 11 matching lines @@
   // Globally unique id for this extension.
   optional string id = 1;
   // The known installed version.
   optional string version = 2;
 
   // Auto-update URL to use for this extension.  May be blank, in
   // which case the default one (i.e., the one for the Chrome
   // Extensions Gallery) is used.
   optional string update_url = 3;
   // Whether or not this extension is enabled.
-  // TODO(yoz): New sync clients will ignore this state, but we must
-  // keep populating it because old clients behave incorrectly if it's
-  // not present. Temporarily, enabled changes will propagate from new
-  // clients to old, but not vice versa. Once all clients are updated to
-  // ignore this field, we can remove it. See crbug.com/303311.
   optional bool enabled = 4;
   // Whether or not this extension is enabled in incognito mode.
   optional bool incognito_enabled = 5;
 
   // The name of the extension.  Used only for debugging.
   optional string name = 6;
 }