Fix GN bootstrap

BUG=none
R=dpranke@chromium.org

Review URL: https://codereview.chromium.org/2236463003 .

Cr-Original-Commit-Position: refs/heads/master@{#411111}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: db9ce41fb93d59a8ec55b43b8efaa027e5fe0060

tools/gn/bootstrap/bootstrap.py

diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index fa81d10..aab92c2 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -373,6 +373,7 @@
       'base/base_switches.cc',
       'base/callback_internal.cc',
       'base/command_line.cc',
+      'base/debug/activity_tracker.cc',
       'base/debug/alias.cc',
       'base/debug/stack_trace.cc',
       'base/debug/task_annotator.cc',