[New Multicolumn] balancer confused by content with top margins.

Source/core/rendering/RenderMultiColumnFlowThread.cpp

 /*
  * Copyright (C) 2012 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 211 matching lines @@
 {
     if (RenderMultiColumnSet* multicolSet = toRenderMultiColumnSet(regionAtBlockOffset(offset))) {
         multicolSet->addForcedBreak(offset);
         if (offsetBreakAdjustment)
             *offsetBreakAdjustment = pageLogicalHeightForOffset(offset) ? pageRemainingLogicalHeightForOffset(offset, IncludePageBoundary) : LayoutUnit();
         return true;
     }
     return false;
 }
 
+bool RenderMultiColumnFlowThread::isPageLogicalHeightKnown() const
+{
+    for (RenderBox* renderer = parentBox()->lastChildBox(); renderer; renderer = renderer->previousSiblingBox()) {
+        if (renderer->isRenderMultiColumnSet())
+            return toRenderMultiColumnSet(renderer)->computedColumnHeight();
+    }
+    // A column set hasn't been created yet. Height may already be known if column-fill is 'auto', though.
+    return !requiresBalancing();
 }
+
+}