Use a reasonable fallback when adding visualization views to the runtime container view.
Use a reasonable fallback when adding visualization views to the runtime container view.

Summary:
We were assuming that target views would be part of the view hierarchy by the time runtime.add was invoked, but this isn't always the case. When there is no parent we'll fall back to a best-guess of the frame being the container view's bounds.

Closes https://github.com/material-motion/material-motion-swift/issues/101

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, markwei

Reviewed By: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, markwei

Subscribers: markwei

Tags: #material_motion

Differential Revision: http://codereview.cc/D3046

material-motion/material-motion-swift,material-motion/material-motion-swift