We use an LRU for this rather than a WeakMap because of how the "no-change" optimization works.
When the frontend polls the backend for an update on the element that's currently inspected, the backend will send a "no-change" message if the element hasn't updated (rendered) since the last time it was asked. In thid case, the frontend cache should reuse the previous (cached) value. Using a WeakMap keyed on Element generally works well for this, since Elements are mutable and stable in the Store. This doens't work properly though when component filters are changed, because this will cause the Store to dump all roots and re-initialize the tree (recreating the Element objects).
So instead we key on Element ID (which is stable in this case) and use an LRU for eviction.
* Restore inspect-element bridge optimizations
When the new Suspense cache was integrated (so that startTransition could be used) I removed a couple of optimizations between the backend and frontend that reduced bridge traffic when e.g. dehydrated paths were inspected for elements that had not rendered since previously inspected. This commit re-adds those optimizations as well as an additional test with a bug fix that I noticed while reading the backend code.
There are two remaining TODO items as of this commit:
- Make inspected element edits and deletes also use transition API
- Don't over-eagerly refresh the cache in our ping-for-updates handler
I will addres both in subsequent commits.
* Poll for update only refreshes cache when there's an update
* Added inline comment
