Remove out-of-date FIXME on collapsing margins

Source/core/rendering/RenderBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1282 matching lines @@
         // i.e., clearance = [height of float] - margin-top".
         setLogicalHeight(child->logicalTop() + childMargins.negativeMarginBefore());
     } else {
         // Increase our height by the amount we had to clear.
         setLogicalHeight(logicalHeight() + heightIncrease);
     }
 
     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.
         setMaxMarginBeforeValues(oldTopPosMargin, oldTopNegMargin);
         marginInfo.setAtBeforeSideOfBlock(false);
 
         // In case the child discarded the before margin of the block we need to reset the mustDiscardMarginBefore flag to the initial value.
         setMustDiscardMarginBefore(style()->marginBeforeCollapse() == MDISCARD);
     }
 
     return yPos + heightIncrease;
 }
 
@@ skipping 1524 matching lines @@
 RenderBlockFlow::RenderBlockFlowRareData& RenderBlockFlow::ensureRareData()
 {
     if (m_rareData)
         return *m_rareData;
 
     m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
     return *m_rareData;
 }
 
 } // namespace WebCore