Code is correct, should fix the spec:

https://github.com/WICG/ResizeObserver/issues/35

@foolip

My code and spec format are similar to IntersectionObserver.

idl files:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/observer/ResizeObserverEntry.idl
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/IntersectionObserverEntry.idl

- both do not define constructor in implementation idl

specs:
https://wicg.github.io/IntersectionObserver/#intersection-observer-entry
https://wicg.github.io/ResizeObserver/#resize-observer-entry-interface

- both define constructor in spec idl
- only ResizeObserver specifies constructor implementation.

What do you suggest I fix?

IntersectionObserverEntry is issue 674519, so filing a spec issue for that too would be a good idea. If there's no particularly good reason to have the constructors, just removing them from the spec seems fine to me.

Reopening to keep track of this until spec and implementation agree.