bi-12 step 01 — The trace ↔ source bridge

Goal

Make tracing a navigation tool, not just a performance tool. This works on stock Chrome with no build.

Tasks

1. Read base/trace_event/builtin_categories.h — roughly 500 category strings. Note the ones relevant to each question you ask.
2. Record a page load with blink, cc, viz, gpu, toplevel.
3. Pick three unfamiliar event names. Grep each literal string in the checkout. Write down what each event actually measures.
4. Confirm devtools.timeline is itself a trace category, and state what follows: the DevTools panel is a curated view over data you can widen.
5. Identify, by name, the events for style recalculation, layout, pre-paint, paint, commit, activation, raster, and presentation. This is the vocabulary the rest of the track uses.

Done when

• Three event names traced back to source
• Pipeline-stage event names written down
• You can state why tracing is rung 3 of the ladder while being faster than rung 1 here