webLocalFirstPaintMaxRawContentBytes property
Small, resource-simple web pages may take their first recorded picture locally instead of waiting for a newly-started render worker. Worker boot is roughly 150 ms in real Chromium while an ordinary text page records in about 10 ms; the full raster still runs through the engine either way. Pages with XObjects or larger content stay on the worker path so image decode and dense interpreter walks never move onto the UI isolate. Set to zero to disable.
Implementation
static int webLocalFirstPaintMaxRawContentBytes = 64 * 1024;