Use new GN features in the build.

third_party/protobuf/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.
 
 if (is_win) {
   config_h_dir = "vsprojects"
 } else {
   config_h_dir = "."
 }
 
 config("protobuf_config") {
   include_dirs = [
     "src",
     config_h_dir,
   ]
   defines = [
     "GOOGLE_PROTOBUF_NO_RTTI",
     "GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER",
   ]
 }
 
-if (component_mode == "shared_library") {
+if (is_component_build) {
   config("protobuf_use_dlls") {
     defines = [ "PROTOBUF_USE_DLLS" ]
   }
 }
 
 # This config should be applied to targets using generated code from the proto
 # compiler. It sets up the include directories properly.
 config("using_proto") {
   include_dirs = [
     "src",
@@ skipping 63 matching lines @@
   public_configs = [
     ":protobuf_config",
 
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 
   cflags = protobuf_lite_cflags
 
   # Required for component builds. See http://crbug.com/172800.
-  if (component_mode == "shared_library") {
+  if (is_component_build) {
     public_configs += [ ":protobuf_use_dlls" ]
     defines = [ "LIBPROTOBUF_EXPORTS" ]
   }
 }
 
 # This is the full, heavy protobuf lib that's needed for c++ .protos that don't
 # specify the LITE_RUNTIME option. The protocol compiler itself (protoc) falls
 # into that category. Do not use in Chrome code.
 
 source_set("protobuf_full") {
@@ skipping 212 matching lines @@
     ":copy_google",
     ":copy_google_protobuf",
     ":copy_google_protobuf_internal",
   ]
 
   # Targets that depend on this should depend on the copied data files.
   data = get_target_outputs(":copy_google")
   data += get_target_outputs(":copy_google_protobuf")
   data += get_target_outputs(":copy_google_protobuf_internal")
 }