This happens when the event in question is generated on non-top level (e.g. within ParseHTML), so it's not picked by InspectorTimelinePanel._innerAddRecordToTimeline, which only checks top-level records.
Created attachment 194846 [details] Patch
Comment on attachment 194846 [details] Patch Is there a test for this?
Created attachment 195292 [details] Patch
(In reply to comment #2) > Is there a test for this? Added.
Committed r147097: <http://trac.webkit.org/changeset/147097>