refactor: rename the atom directory to shell

shell/browser/child_web_contents_tracker.cc

@@ -0,0 +1,14 @@
+// Copyright (c) 2019 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "atom/browser/child_web_contents_tracker.h"
+
+namespace atom {
+
+ChildWebContentsTracker::ChildWebContentsTracker(
+    content::WebContents* web_contents) {}
+
+WEB_CONTENTS_USER_DATA_KEY_IMPL(ChildWebContentsTracker)
+
+}  // namespace atom