Before this commit, the App destroy method would not destroy everything
synchronously. The code scheduled a flush, which is asynchronous, to
finally clean up the task lists, and destroy the cancelled nodes. But
this is not really good for tests: we need a stronger guarantee that
nothing will happen after the destroy.
With this commit, we simply call the processTask method immediately
after destroying the root component, so all cancelled nodes will be
destroyed immediately.
Previously, attempting to mount an app in an iframe would crash, saying
that the target is not a valid DOM element, this is because instanceof
checks do not work cross-frame as global objects do not have the same
identity in frames as with the main window. This commit fixes that by
making sure the target is an instance of HTMLElement of the
corresponding window, and checks that the corresponding document body
contains it.
Samuel Degueldre