We currently track active, hidden, and frozen, but not passive (see https://cs.chromium.org/chromium/src/third_party/blink/renderer/platform/scheduler/public/page_lifecycle_state.h).

Adding passive state would make Blink in sync with page lifecycle API (https://github.com/WICG/page-lifecycle), and allow us to expose the proper states to developers for debugging (i.e. chrome://discards) based on Blink state.

In the future, frames in the passive state maybe frozen, though not pages in the passive state.