Correct remaining LayoutUnit misuse in RenderReplaced and RenderFlexibleBox

Correct remaining LayoutUnit misuse in RenderReplaced and RenderFlexibleBox
https://bugs.webkit.org/show_bug.cgi?id=82899

Reviewed by Darin Adler.

Removing remaining LayoutUnit misuse and compiler errors that exist in RenderReplaced
and RenderFlexibleBox once LayoutUnit becomes sub-pixel.

No new tests. No change in behavior.

* rendering/RenderFlexibleBox.cpp:
(WebCore::RenderFlexibleBox::repositionLogicalHeightDependentFlexItems): Switching
a raw zero in a ternary operation to zeroLayoutUnit.
(WebCore::RenderFlexibleBox::applyStretchAlignmentToChild): Ditto for std::max.
* rendering/RenderReplaced.cpp:
(WebCore::RenderReplaced::paint): Adding missing pixel snapping before painting.
(WebCore::RenderReplaced::computeReplacedLogicalWidth): Like above, switching
a raw zero to zeroLayoutUnit.
(WebCore::RenderReplaced::computePreferredLogicalWidths): Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@112936 268f45cc-cd09-0410-ab3c-d52691b4dbfc