$watchCollection listener is not returning old value for objects

[gizm0bill]

Both objects are the same in the callback.
As I see in your specs you are only testing the new value and in the code there is something like: "copy the items to oldValue and look for changes."

Please explain, thanks!

[gonzaloruizdevilla]

I made a PR for this: #3865. It's related to issue #1751.
This commit should fix it: gonzaloruizdevilla@bf69ca0
Milestone for this is Post-1.2

[IgorMinar]

dupe of #2621