Use list_dart_files.py instead of list_files.py in GN build.

pkg/BUILD.gn

 # Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import("../utils/create_timestamp.gni")
 
 template("make_third_party_pkg_files_stamp") {
-  assert(defined(invoker.pattern), "Must define the file pattern")
   assert(defined(invoker.id), "Must define the stamp file id")
   path = rebase_path("../third_party/pkg")
   if (defined(invoker.path)) {
     path = invoker.path
   }
   id = invoker.id
   create_timestamp_file(target_name) {
-    pattern = invoker.pattern
+    if (defined(invoker.pattern)) {
+      pattern = invoker.pattern
+    }
     path = path
     new_base = "//"
     output = "$target_gen_dir/third_party_pkg_files_$id.stamp"
   }
 }
 
 make_third_party_pkg_files_stamp("make_third_party_pkg_files_0_stamp") {
-  pattern = "^(?!.*/test/).*(?<!_test)[.]dart\$"
   path = rebase_path(".")
   id = "0"
 }
 
 make_third_party_pkg_files_stamp("make_third_party_pkg_files_1_stamp") {
-  pattern = "^(?!.*_test\.dart).*[a-k]\.dart\$"
+  pattern = "[a-k].*"
   id = "1"
 }
 
 make_third_party_pkg_files_stamp("make_third_party_pkg_files_2_stamp") {
-  pattern = "^(?!.*_test\.dart).*[l-r]\.dart\$"
+  pattern = "[l-r].*"
   id = "2"
 }
 
 make_third_party_pkg_files_stamp("make_third_party_pkg_files_3_stamp") {
-  pattern = "^(?!.*_test\.dart).*[^a-r]\.dart\$"
+  pattern = "[s-z].*"
   id = "3"
 }
 
 action("pkg_files_stamp") {
   deps = [
     ":make_third_party_pkg_files_0_stamp",
     ":make_third_party_pkg_files_1_stamp",
     ":make_third_party_pkg_files_2_stamp",
     ":make_third_party_pkg_files_3_stamp",
   ]
 
   stamp0_outputs = get_target_outputs(":make_third_party_pkg_files_0_stamp")
   stamp1_outputs = get_target_outputs(":make_third_party_pkg_files_1_stamp")
   stamp2_outputs = get_target_outputs(":make_third_party_pkg_files_2_stamp")
   stamp3_outputs = get_target_outputs(":make_third_party_pkg_files_3_stamp")
 
-  inputs = ["../tools/list_files.py"] +
-      stamp0_outputs +
-      stamp1_outputs +
-      stamp2_outputs +
-      stamp3_outputs
+  inputs = stamp0_outputs +
+           stamp1_outputs +
+           stamp2_outputs +
+           stamp3_outputs
 
   outputs = [
     "$root_gen_dir/pkg_files.stamp"
   ]
 
   script = "../tools/create_timestamp_file.py"
   args = [
     rebase_path("$root_gen_dir/pkg_files.stamp"),
   ]
 }