Switched sync protobufs to use "heavy" protobufs.

chrome/browser/sync/protocol/theme_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 themes.
 
 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 theme sync objects.
 message ThemeSpecifics {
   // If set, we're using a custom theme and all custom_* fields should be
   // present.  If not set, we use the default or system theme (see below)
   // and all custom_* fields should be omitted.
@@ skipping 11 matching lines @@
 
   // Custom-theme-specific fields.
   optional string custom_theme_name = 3;
   optional string custom_theme_id = 4;
   optional string custom_theme_update_url = 5;
 }
 
 extend EntitySpecifics {
   optional ThemeSpecifics theme = 41210;
 }