Make View's defaults inheritable and extendable

Now when children of View define the `defaults` property, properties of
`defaults` of the parent are preserved if the child doesn't override
them.

Previous behaviour led to missing close button message in most overlays,
which suggests that extending defaults in this new way may be more
intuitive, if slightly more magical.

Change-Id: Id6bb5a89dea33200ea9cf35535644bde54d8820e
Merge "Make View's defaults inheritable and extendable"