Switched sync protobufs to use "heavy" protobufs.

chrome/browser/sync/protocol/extension_specifics.proto

 // Copyright (c) 2010 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.
 
 syntax = "proto2";
 
-option optimize_for = LITE_RUNTIME;
+// TODO(akalin): Re-enable this once LITE_RUNTIME supports preserving
+// unknown fields.
+
+// option optimize_for = LITE_RUNTIME;
 
 package sync_pb;
 
 import "sync.proto";
 
 // Properties of extension sync objects.
 //
 // Merge policy: the settings for the higher version number win; in
 // the case of a tie, server wins.
 message ExtensionSpecifics {
@@ skipping 11 matching lines @@
   // 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;
 }
 
 extend EntitySpecifics {
   optional ExtensionSpecifics extension = 48119;
 }