[LFC][Floating] FloatBox -> FloatAvoider

[LFC][Floating] FloatBox -> FloatAvoider
https://bugs.webkit.org/show_bug.cgi?id=188941

Reviewed by Antti Koivisto.

This is in preparation for the float avoidance feature where formatting context root boxes avoid existing floats.

* Sources.txt:
* WebCore.xcodeproj/project.pbxproj:
* layout/displaytree/DisplayBox.h:
* layout/floats/FloatAvoider.cpp: Renamed from Source/WebCore/layout/floats/FloatBox.cpp.
(WebCore::Layout::FloatAvoider::FloatAvoider):
(WebCore::Layout::FloatAvoider::initializePosition):
(WebCore::Layout::FloatAvoider::isLeftAligned const):
(WebCore::Layout::FloatAvoider::setLeft):
(WebCore::Layout::FloatAvoider::setTopLeft):
(WebCore::Layout::FloatAvoider::resetVertically):
(WebCore::Layout::FloatAvoider::resetHorizontally):
(WebCore::Layout::FloatAvoider::topLeftInContainingBlock const):
* layout/floats/FloatAvoider.h: Renamed from Source/WebCore/layout/floats/FloatBox.h.
(WebCore::Layout::FloatAvoider::top const):
(WebCore::Layout::FloatAvoider::left const):
(WebCore::Layout::FloatAvoider::marginTop const):
(WebCore::Layout::FloatAvoider::marginLeft const):
(WebCore::Layout::FloatAvoider::marginBottom const):
(WebCore::Layout::FloatAvoider::marginRight const):
(WebCore::Layout::FloatAvoider::rectWithMargin const):
(WebCore::Layout::FloatAvoider::setTop):
* layout/floats/FloatingContext.cpp:
(WebCore::Layout::FloatingContext::positionForFloat const):
(WebCore::Layout::FloatingContext::floatingPosition const):
* layout/floats/FloatingContext.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@235352 268f45cc-cd09-0410-ab3c-d52691b4dbfc