Fix GN bootstrap

BUG=551343
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/1950183007 .

Cr-Original-Commit-Position: refs/heads/master@{#392029}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8c8c59ed41a27c4f7b914a7943f2c8460f004412
diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index 2262ab4..3d99636 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -291,6 +291,7 @@
       'base/thread_task_runner_handle.cc',
       'base/threading/non_thread_safe_impl.cc',
       'base/threading/post_task_and_reply_impl.cc',
+      'base/threading/sequenced_task_runner_handle.cc',
       'base/threading/sequenced_worker_pool.cc',
       'base/threading/simple_thread.cc',
       'base/threading/thread.cc',