When including a component in a template, the component's host element
is immediately appended as child of the parent node upon creation.
Hence, `hostElement.parentNode` will be a valid reference. However, if
the parent component is being inserted as an embedded view—through
`ngIf` for example—then the parent's node itself will not have been
inserted yet. This means that we cannot properly determine the position
of the transition namespace, as any `containsElement` check will return
false given that the partial DOM tree has not been inserted yet, even
though it will be contained within an existing transition namespace once
the partial tree is attached.
This commit fixes the issue by not just looking at the existence of a
parent node, but rather a more extensive check using the driver's
`containsElement` method.
PR Close#19854
e27ac018ed