Ownership between WebPlaybackSessionInterfaceMac and WebPlaybackControlsManager is...

Ownership between WebPlaybackSessionInterfaceMac and WebPlaybackControlsManager is backwards.
https://bugs.webkit.org/show_bug.cgi?id=159441

Reviewed by Eric Carlson.

The WebPlaybackControlsManager should own the WebPlaybackSessionInterfaceMac, and not
vice versa.

* platform/mac/WebPlaybackControlsManager.h:
* platform/mac/WebPlaybackControlsManager.mm:
(-[WebPlaybackControlsManager webPlaybackSessionInterfaceMac]):
(-[WebPlaybackControlsManager setWebPlaybackSessionInterfaceMac:]):
* platform/mac/WebPlaybackSessionInterfaceMac.h:
* platform/mac/WebPlaybackSessionInterfaceMac.mm:
(WebCore::WebPlaybackSessionInterfaceMac::playBackControlsManager):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@202908 268f45cc-cd09-0410-ab3c-d52691b4dbfc