Resource Timing Buffer/Secondary Buffer properties have vague location

https://w3c.github.io/resource-timing/#sec-extensions-performance-interface says "Each ECMAScript global environment has ..." followed by a bunch of buffer and integer properties.

• A resource timing buffer size limit which should initially be 250 or greater.
• A resource timing buffer current size which is initially 0.
• A resource timing buffer full event pending flag which is initially false.
• A resource timing secondary buffer current size which is initially 0.
• A resource timing secondary buffer to store PerformanceResourceTiming objects that is initially empty.

The statement "ECMAScript global environment" links to https://webidl.spec.whatwg.org/#es-environment, which is not nearly specific enough for an implementation to decide where to place the properties.

I would expect them to be defined as existing on one of:

• Every WindowOrWorkerGlobalScope instance
• Every HTML Environment Settings Object
• Certain categories of ESOs
• Each Agent
• Each Agent Cluster
• One instance for the User Agent itself (still vague, but better vague)

What entity is supposed to own these buffers? cc @noamr