GN: Fix bootstrap.py

//base/thread_task_runner_handle.cc was moved into //base/threading/.

Also for the build to succeed it now needs //base/files/important_file_writer.cc as well.

R=brettw@chromium.org

Review-Url: https://codereview.chromium.org/1972093002
Cr-Original-Commit-Position: refs/heads/master@{#394528}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f80bd170f853b83631da9a17803bd919a7b17204
diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index 3d99636..fea9312 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -224,6 +224,7 @@
       'base/files/file_path_constants.cc',
       'base/files/file_tracing.cc',
       'base/files/file_util.cc',
+      'base/files/important_file_writer.cc',
       'base/files/memory_mapped_file.cc',
       'base/files/scoped_file.cc',
       'base/hash.cc',
@@ -288,7 +289,6 @@
       'base/third_party/dmg_fp/g_fmt.cc',
       'base/third_party/icu/icu_utf.cc',
       'base/third_party/nspr/prtime.cc',
-      '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',
@@ -300,6 +300,7 @@
       'base/threading/thread_id_name_manager.cc',
       'base/threading/thread_local_storage.cc',
       'base/threading/thread_restrictions.cc',
+      'base/threading/thread_task_runner_handle.cc',
       'base/threading/worker_pool.cc',
       'base/time/time.cc',
       'base/timer/elapsed_timer.cc',