Allow TransitionWithPresentation to return nil for conditional presentation.

Authored by featherless on Tue, May 16, 12:31 PM.

Description

Allow TransitionWithPresentation to return nil for conditional presentation.

Summary: Returning nil means no presentation controller will be used.

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/D3229