[LayoutReloaded] Remove FormattingContext::absoluteMarginBox

[LayoutReloaded] Remove FormattingContext::absoluteMarginBox
https://bugs.webkit.org/show_bug.cgi?id=184213

Reviewed by Antti Koivisto.

Display.Box already has the margin values.

* LayoutReloaded/FormattingContext/FloatingContext.js:
(FloatingContext.prototype._positionForFloating):
(FloatingContext.prototype._addFloatingBox):
(FloatingContext.prototype._mapMarginBoxToFormattingRoot):
(FloatingContext.prototype._formattingRoot):
* LayoutReloaded/FormattingContext/FormattingContext.js:
(FormattingContext.prototype.absoluteMarginBox): Deleted.
* LayoutReloaded/Utils.js:
(Utils.marginBox):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@230136 268f45cc-cd09-0410-ab3c-d52691b4dbfc