This should show how to make a Canvas resize whenever the actor that
uses it as content changes size. For good measure, it also shows how to
coalesce multiple allocations into one Canvas resize through a timeout
source.
The example code that is meant to be XIncluded into the API reference
should not be part of the interactive test suite: it's code that it is
meant to be used as a reference implementation - whereas the interactive
test suite should be allowed to be lean and test behaviour even in nasty
ways. In short: the test suite should not be the place where we show off
idiomatic code for educational purposes.