All subscribers are working in thread-safe manners (they either takelocks to clear caches, or use existing batching/threading primitives toqueue new work).

Subscribers were already thread safe. I've also removed the IMPORTANTwarning since it seems quite stale -- this is already in a delayed queueso it's not really clear what it meant.

I'm unable to figure out what the intent was here -- it clears the listbut only on a SolutionChanged event, which is the type of eventraised if multiple projects are modified at once in a single workspacechange -- any other type of event would have a more specific kind.I could imagine the intent might have been for solution close, butthen I can imagine scenarios where the user might have pasted a stackand now needs to switch the solution to navigate from the stack.Since this likely never ran, I'm just deleting it.

If the user expands a node in a CPS project wanting to look at thediagnostics under an analyzer, but we haven't been told about thatanalyzer let, we stick a WorkspaceChanged handler there to find it onceit comes back. We were hopping to the UI thread to see if theCanonicalName of the item could have changed, but that's not reallygoing to happen ever for these items, so we can just grab it onceduring creation and be done with it.

This looks to be safely callable from any thread.