bi-02 step 01 — Process and thread census

Goal

Convert the architecture diagram from a claim into something you have observed on your own machine.

Process census. Open Chrome's own task manager. Load a trivial page and record which process types exist. Then load a page that paints heavily, then one with a cross-site iframe. Record the deltas.
Site vs origin. Confirm that a cross-site iframe creates an additional renderer and that a same-site, cross-origin iframe does not. Explain the result using SiteInstance and the definition of site (scheme + eTLD+1).
Browsing context group. Open a popup with window.open(), then again with rel="noopener". Observe the process allocation difference and explain it via BrowsingInstance.
Thread census. From a Perfetto trace of a page load, list every thread in the renderer process by name. Identify main, compositor, raster pool, and IO. (With a local build, thread backtrace all in lldb gives the same list faster.)
Write the diagram from memory, then correct it against what you observed. The corrections are the output.

Process counts recorded for three page types
Cross-site vs same-site iframe difference demonstrated and explained
noopener effect observed
Renderer thread names written down — you will grep for these for the rest of the track