Remove out-of-date FIXME on collapsing margins

Source/core/rendering/RenderBlockFlow.cpp

Index: Source/core/rendering/RenderBlockFlow.cpp
diff --git a/Source/core/rendering/RenderBlockFlow.cpp b/Source/core/rendering/RenderBlockFlow.cpp
index a01af7a465790dd182323d219f4d78ebe554133b..d4b14145b62efc43b8ca1c303e90f9eb6ec754f7 100644
--- a/Source/core/rendering/RenderBlockFlow.cpp
+++ b/Source/core/rendering/RenderBlockFlow.cpp
@@ -1298,9 +1298,6 @@ LayoutUnit RenderBlockFlow::clearFloatsIfNeeded(RenderBox* child, MarginInfo& ma
     if (marginInfo.canCollapseWithMarginBefore()) {
         // We can no longer collapse with the top of the block since a clear
         // occurred. The empty blocks collapse into the cleared block.
-        // FIXME: This isn't quite correct. Need clarification for what to do
-        // if the height the cleared block is offset by is smaller than the
-        // margins involved.

[Julien - ping for review, 2014/03/19 00:56:24]

Removing this FIXME is OK but are we matching CSS 2.1's behavior? Is this
covered by any cases?

By removing this FIXME, we may be losing the fact that this code needs to be
updated. I am fine with either fixing (along with appropriate testing) or just
adding an up-to-date FIXME.

         setMaxMarginBeforeValues(oldTopPosMargin, oldTopNegMargin);
         marginInfo.setAtBeforeSideOfBlock(false);