[New Multicolumn] Lay out flow thread again when multicol container height changes.

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 182 matching lines @@
     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
         if (flowThread->computeColumnCountAndWidth())
             return true;
     }
     return relayoutChildren;
 }
 
 void RenderBlockFlow::checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight)
 {
     if (RenderMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
-        // We don't actually update any of the variables. We just subclassed to adjust our column height.
         updateLogicalHeight();
+        pageLogicalHeightChanged = contentLogicalHeight() != flowThread->columnHeightAvailable();
         flowThread->setColumnHeightAvailable(std::max<LayoutUnit>(contentLogicalHeight(), 0));
         setLogicalHeight(0);
     } else if (hasColumns()) {
         ColumnInfo* colInfo = columnInfo();
 
         if (!pageLogicalHeight) {
             LayoutUnit oldLogicalHeight = logicalHeight();
             setLogicalHeight(0);
             // We need to go ahead and set our explicit page height if one exists, so that we can
             // avoid doing two layout passes.
@@ skipping 129 matching lines @@
 {
     LayoutUnit oldLeft = logicalLeft();
     if (updateLogicalWidthAndColumnWidth())
         relayoutChildren = true;
 
     rebuildFloatsFromIntruding();
 
     bool pageLogicalHeightChanged = false;
     bool hasSpecifiedPageLogicalHeight = false;
     checkForPaginationLogicalHeightChange(pageLogicalHeight, pageLogicalHeightChanged, hasSpecifiedPageLogicalHeight);
+    if (pageLogicalHeightChanged)
+        relayoutChildren = true;
 
     LayoutStateMaintainer statePusher(*this, locationOffset(), pageLogicalHeight, pageLogicalHeightChanged, columnInfo());
 
     // We use four values, maxTopPos, maxTopNeg, maxBottomPos, and maxBottomNeg, to track
     // our current maximal positive and negative margins. These values are used when we
     // are collapsed with adjacent blocks, so for example, if you have block A and B
     // collapsing together, then you'd take the maximal positive margin from both A and B
     // and subtract it from the maximal negative margin from both A and B to get the
     // true collapsed margin. This algorithm is recursive, so when we finish layout()
     // our block knows its current maximal positive/negative values.
@@ skipping 2433 matching lines @@
 RenderBlockFlow::RenderBlockFlowRareData& RenderBlockFlow::ensureRareData()
 {
     if (m_rareData)
         return *m_rareData;
 
     m_rareData = adoptPtr(new RenderBlockFlowRareData(this));
     return *m_rareData;
 }
 
 } // namespace WebCore