Add "bundle_data" target as first step for adding bundle support to gn.

tools/gn/BUILD.gn

 # Copyright (c) 2013 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("//testing/test.gni")
 
 defines = [ "GN_BUILD" ]
 
 static_library("gn_lib") {
   configs += [ "//build/config:precompiled_headers" ]
 
   sources = [
     "action_target_generator.cc",
     "action_target_generator.h",
     "action_values.cc",
     "action_values.h",
     "args.cc",
     "args.h",
     "binary_target_generator.cc",
     "binary_target_generator.h",
     "build_settings.cc",
     "build_settings.h",
     "builder.cc",
     "builder.h",
     "builder_record.cc",
     "builder_record.h",
+    "bundle_data_target_generator.cc",
+    "bundle_data_target_generator.h",
     "c_include_iterator.cc",
     "c_include_iterator.h",
     "command_args.cc",
     "command_check.cc",
     "command_clean.cc",
     "command_desc.cc",
     "command_format.cc",
     "command_gen.cc",
     "command_help.cc",
     "command_ls.cc",
@@ skipping 66 matching lines @@
     "loader.cc",
     "loader.h",
     "location.cc",
     "location.h",
     "ninja_action_target_writer.cc",
     "ninja_action_target_writer.h",
     "ninja_binary_target_writer.cc",
     "ninja_binary_target_writer.h",
     "ninja_build_writer.cc",
     "ninja_build_writer.h",
+    "ninja_bundle_data_target_writer.cc",
+    "ninja_bundle_data_target_writer.h",
     "ninja_copy_target_writer.cc",
     "ninja_copy_target_writer.h",
     "ninja_group_target_writer.cc",
     "ninja_group_target_writer.h",
     "ninja_target_writer.cc",
     "ninja_target_writer.h",
     "ninja_toolchain_writer.cc",
     "ninja_toolchain_writer.h",
     "ninja_utils.cc",
     "ninja_utils.h",
@@ skipping 184 matching lines @@
     "format_test_data/",
   ]
 
   deps = [
     ":gn_lib",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 }