JavaFX failures due to creating weak references to value objects

[Kevin Rushforth]

I posted the following to the valhalla-dev alias:

https://mail.openjdk.org/archives/list/valhalla-...@openjdk.org/thread/TD7AQH4SNRS4QAQAXTISKIERNK6LINYB/
I don't want to discuss the overall issues in two different places, so 
if you have general comments on the interaction of value objects and 
JavaFX, I invite you to reply to the valhalla-dev thread I started.

If there are comments specific to JavaFX (e.g., a discussion of whether 
/ how we might be able to eliminate our need for weak references to 
items in ListView, etc; or a discussion of the specifics of a 
WeakReferenceWrapper  implementation for use by the native WebView Java 
<--> JS bridge), that would be better discussed here.

-- Kevin