- A built-in typed-array constructor set as a view's `constructor` is its
own species, as the getter it inherits from %TypedArray% returns it:
`u8.constructor = Float64Array; u8.map(f)` makes a Float64Array. An own
Symbol.species on the constructor still wins.
- TypedArray.prototype.slice with a species constructor creates the
result first and then copies the source's current elements, up to its
current length: a constructor that changes the source is seen.
- Object.defineProperty on a typed-array element reads the descriptor as
ToPropertyDescriptor does, through its getters and in its order, and
throws a TypeError for a primitive descriptor or an accessor with a
value. The generic object path shares the same reader.