Improve WebKitLegacy video fullscreen animation begin and end rects.

Improve WebKitLegacy video fullscreen animation begin and end rects.
https://bugs.webkit.org/show_bug.cgi?id=175152
rdar://problem/32840576

Patch by Jeremy Jones <jeremyj@apple.com> on 2017-08-03
Reviewed by Eric Carlson.

No new tests, becuase this change has no effect on the DOM.

This change uses different rects for fullscreen animation to prevent the animation
from failing, and to improve the aesthetics of the animation.

* platform/mac/WebVideoFullscreenController.mm:
(frameExpandedToRatioOfFrame):
(-[WebVideoFullscreenController enterFullscreen:]):
(-[WebVideoFullscreenController exitFullscreen]):
(-[WebVideoFullscreenWindow animateFromRect:toRect:withSubAnimation:controllerAction:]):
(constrainFrameToRatioOfFrame): Deleted.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@220248 268f45cc-cd09-0410-ab3c-d52691b4dbfc