Say that a shared request belongs to the reader which asked for it

Author: Archmonger

CHANGELOG.md

@@ -42,7 +42,7 @@ Don't forget to remove deprecated code on each major release!
     - `throttle` caps the rate how often an event is allowed to execute. No default; opt in per event.
 - Added a live event proxy which lets event handlers read properties from, and call methods on, the browser objects which triggered them (ex. `await event.target.value`, `await event.target.focus()`) rather than being limited to whatever was serializable at the moment the event was dispatched.
     - Only an id and the event's `type` travel with the event. Whatever a handler reaches past is fetched from the browser on demand, one round trip at a time, and resolved against the object itself.
-    - Properties which are in flight at the same moment go out as a single message, and `await event.read("target.value", "key")` reads several at once.
+    - Properties which are in flight at the same moment go out as a single message, and `await event.read("target.value", "key")` reads several at once. Two handlers which want the same property at the same moment share that one message, and one which walks away from an answer it only borrowed leaves the message in place for the one which asked.
     - A read belongs to the moment it is awaited: it reports the current state of the browser object, not the state it held when the event was dispatched.
     - Whatever a read found is remembered against the event, so reading one property twice costs one round trip - and a handler which wants what the browser holds by now asks again with `await event.read("target.value", refresh=True)`.
     - Whatever comes back out of a method call can be walked too: the page keeps what the call answered for as long as it keeps the event, so a reference into a result resolves against that answer rather than against the method.