Update LayoutUnit usage in ColumnInfo and RenderFrameSet

Update LayoutUnit usage in ColumnInfo and RenderFrameSet
https://bugs.webkit.org/show_bug.cgi?id=77914

Reviewed by Eric Seidel.

Updating ColumnInfo and RenderFrameSet to use LayoutUnits
instead of directly referencing integers for locations and
distances.

No new tests. No changed behavior.

* rendering/ColumnInfo.h:
(WebCore::ColumnInfo::forcedBreakOffset):
(WebCore::ColumnInfo::maximumDistanceBetweenForcedBreaks):
(ColumnInfo):
* rendering/RenderFrameSet.cpp:
(WebCore::RenderFrameSet::paintColumnBorder):
(WebCore::RenderFrameSet::paintRowBorder):
* rendering/RenderFrameSet.h:
(RenderFrameSet):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107009 268f45cc-cd09-0410-ab3c-d52691b4dbfc