Update modal dialog example to make use of a presentation controller.

Authored by featherless on May 18 2017, 5:10 PM.

Description

Update modal dialog example to make use of a presentation controller.

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, Material Motion, randcode-generator

Reviewed By: randcode-generator

Tags: Material Motion

Differential Revision: http://codereview.cc/D3242