GitLab

These were mostly for the convenience of layout tests, rarely used in the
prod code. Let's keep TimelineModel.Record() a thin wrapper that just adds
hierarchy to trace events and keep timeline-specific logic away from it,
since it has to work for bare trace events most of the time.

BUG=

Review URL: https://codereview.chromium.org/1315373005

git-svn-id: svn://svn.chromium.org/blink/trunk@202020 bbb929c8-8fbe-4397-9dbb-9b2b20218538