CONSOLE MESSAGE: line 482: callback not yet supported

PASS idl_test setup 
PASS IntersectionObserver interface: existence and properties of interface object 
PASS IntersectionObserver interface object length 
PASS IntersectionObserver interface object name 
PASS IntersectionObserver interface: existence and properties of interface prototype object 
PASS IntersectionObserver interface: existence and properties of interface prototype object's "constructor" property 
PASS IntersectionObserver interface: existence and properties of interface prototype object's @@unscopables property 
PASS IntersectionObserver interface: attribute root 
PASS IntersectionObserver interface: attribute rootMargin 
PASS IntersectionObserver interface: attribute thresholds 
PASS IntersectionObserver interface: operation observe(Element) 
PASS IntersectionObserver interface: operation unobserve(Element) 
PASS IntersectionObserver interface: operation disconnect() 
PASS IntersectionObserver interface: operation takeRecords() 
PASS IntersectionObserver must be primary interface of observer 
PASS Stringification of observer 
PASS IntersectionObserver interface: observer must inherit property "root" with the proper type 
PASS IntersectionObserver interface: observer must inherit property "rootMargin" with the proper type 
FAIL IntersectionObserver interface: observer must inherit property "thresholds" with the proper type assert_true: Value should be frozen expected true got false
PASS IntersectionObserver interface: observer must inherit property "observe(Element)" with the proper type 
PASS IntersectionObserver interface: calling observe(Element) on observer with too few arguments must throw TypeError 
PASS IntersectionObserver interface: observer must inherit property "unobserve(Element)" with the proper type 
PASS IntersectionObserver interface: calling unobserve(Element) on observer with too few arguments must throw TypeError 
PASS IntersectionObserver interface: observer must inherit property "disconnect()" with the proper type 
PASS IntersectionObserver interface: observer must inherit property "takeRecords()" with the proper type 
PASS IntersectionObserverEntry interface: existence and properties of interface object 
PASS IntersectionObserverEntry interface object length 
PASS IntersectionObserverEntry interface object name 
PASS IntersectionObserverEntry interface: existence and properties of interface prototype object 
PASS IntersectionObserverEntry interface: existence and properties of interface prototype object's "constructor" property 
PASS IntersectionObserverEntry interface: existence and properties of interface prototype object's @@unscopables property 
PASS IntersectionObserverEntry interface: attribute time 
PASS IntersectionObserverEntry interface: attribute rootBounds 
PASS IntersectionObserverEntry interface: attribute boundingClientRect 
PASS IntersectionObserverEntry interface: attribute intersectionRect 
PASS IntersectionObserverEntry interface: attribute isIntersecting 
PASS IntersectionObserverEntry interface: attribute intersectionRatio 
PASS IntersectionObserverEntry interface: attribute target