GN Windows component build fixes.

sync/protocol/BUILD.gn

 # Copyright 2014 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.
 
 import("//third_party/protobuf/proto_library.gni")
 
-proto_library("protocol") {
+# This must be a component for the dependency structure we have now, but the
+# proto_library generates a source set. Link those into a component.
+component("protocol") {
+  public_deps = [
+    ":protocol_internal",
+  ]
+}
+
+proto_library("protocol_internal") {
+  visibility = [ ":protocol" ]
+
   sources = [
     "app_list_specifics.proto",
     "app_notification_specifics.proto",
     "app_setting_specifics.proto",
     "app_specifics.proto",
     "article_specifics.proto",
     "attachments.proto",
     "autofill_specifics.proto",
     "bookmark_specifics.proto",
     "client_commands.proto",
@@ skipping 30 matching lines @@
     "wifi_credential_specifics.proto",
   ]
 
   cc_generator_options = "dllexport_decl=SYNC_PROTO_EXPORT:"
   cc_include = "sync/protocol/sync_proto_export.h"
 
   defines = [ "SYNC_PROTO_IMPLEMENTATION" ]
 
   extra_configs = [ "//build/config/compiler:wexit_time_destructors" ]
 }