Don't eat margins when column height isn't yet known.

Source/core/layout/LayoutBlockFlow.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 1293 matching lines @@
             marginInfo.clearMargin();
         }
 
         if (marginInfo.margin())
             marginInfo.setHasMarginAfterQuirk(hasMarginAfterQuirk(&child));
     }
 
     // If margins would pull us past the top of the next page, then we need to pull back and pretend like the margins
     // collapsed into the page edge.
     LayoutState* layoutState = view()->layoutState();
-    if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTop > beforeCollapseLogicalTop) {
+    if (layoutState->isPaginated() && isPageLogicalHeightKnown(beforeCollapseLogicalTop) && logicalTop > beforeCollapseLogicalTop) {
         LayoutUnit oldLogicalTop = logicalTop;
         logicalTop = std::min(logicalTop, nextPageLogicalTop(beforeCollapseLogicalTop));
         setLogicalHeight(logicalHeight() + (logicalTop - oldLogicalTop));
     }
 
     if (previousBlockFlow) {
         // If |child| is a self-collapsing block it may have collapsed into a previous sibling and although it hasn't reduced the height of the parent yet
         // any floats from the parent will now overhang.
         LayoutUnit oldLogicalHeight = logicalHeight();
         setLogicalHeight(logicalTop);
@@ skipping 200 matching lines @@
         }
 
         // Collapse the result with our current margins.
         if (!discardMarginBefore)
             logicalTopEstimate += std::max(marginInfo.positiveMargin(), positiveMarginBefore) - std::max(marginInfo.negativeMargin(), negativeMarginBefore);
     }
 
     // Adjust logicalTopEstimate down to the next page if the margins are so large that we don't fit on the current
     // page.
     LayoutState* layoutState = view()->layoutState();
-    if (layoutState->isPaginated() && layoutState->pageLogicalHeight() && logicalTopEstimate > logicalHeight())
+    if (layoutState->isPaginated() && isPageLogicalHeightKnown(logicalHeight()) && logicalTopEstimate > logicalHeight())
         logicalTopEstimate = std::min(logicalTopEstimate, nextPageLogicalTop(logicalHeight()));
 
     logicalTopEstimate += getClearDelta(&child, logicalTopEstimate);
 
     estimateWithoutPagination = logicalTopEstimate;
 
     if (layoutState->isPaginated()) {
         // If the object has a page or column break value of "before", then we should shift to the top of the next page.
         logicalTopEstimate = applyBeforeBreak(child, logicalTopEstimate);
 
@@ skipping 1604 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = (style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height();
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink