Multicol: Min-height should have no effect if content is taller and height is auto.

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 191 matching lines @@
     if (LayoutMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
         if (flowThread->needsNewWidth())
             return true;
     }
     return relayoutChildren;
 }
 
 void LayoutBlockFlow::checkForPaginationLogicalHeightChange(LayoutUnit& pageLogicalHeight, bool& pageLogicalHeightChanged, bool& hasSpecifiedPageLogicalHeight)
 {
     if (LayoutMultiColumnFlowThread* flowThread = multiColumnFlowThread()) {
-        LogicalExtentComputedValues computedValues;
-        computeLogicalHeight(LayoutUnit(), logicalTop(), computedValues);
-        LayoutUnit columnHeight = computedValues.m_extent - borderAndPaddingLogicalHeight() - scrollbarLogicalHeight();
+        // Calculate the non-auto content box height, or set it to 0 if it's auto. We need to know
+        // this before layout, so that we can figure out where to insert column breaks. We also
+        // treat LayoutView (which may be paginated, which uses the multicol implmentation) as
+        // having non-auto height, since its height is deduced from the viewport height. We use
+        // computeLogicalHeight() to calculate the content box height. That method will clamp
+        // against max-height and min-height. Since we're now at the beginning of layout, and we
+        // don't know the actual height of the content yet, only call that method when height is
+        // definite, or we might fool ourselves into believing that columns have a definite height
+        // when they in fact don't.
+        LayoutUnit columnHeight;
+        if (hasDefiniteLogicalHeight() || isLayoutView()) {
+            LogicalExtentComputedValues computedValues;
+            computeLogicalHeight(LayoutUnit(), logicalTop(), computedValues);
+            columnHeight = computedValues.m_extent - borderAndPaddingLogicalHeight() - scrollbarLogicalHeight();
+        }
         pageLogicalHeightChanged = columnHeight != flowThread->columnHeightAvailable();
-        flowThread->setColumnHeightAvailable(std::max<LayoutUnit>(columnHeight, 0));
+        flowThread->setColumnHeightAvailable(std::max(columnHeight, LayoutUnit()));
     } else if (isLayoutFlowThread()) {
         LayoutFlowThread* flowThread = toLayoutFlowThread(this);
 
         // FIXME: This is a hack to always make sure we have a page logical height, if said height
         // is known. The page logical height thing in LayoutState is meaningless for flow
         // thread-based pagination (page height isn't necessarily uniform throughout the flow
         // thread), but as long as it is used universally as a means to determine whether page
         // height is known or not, we need this. Page height is unknown when column balancing is
         // enabled and flow thread height is still unknown (i.e. during the first layout pass). When
         // it's unknown, we need to prevent the pagination code from assuming page breaks everywhere
@@ skipping 2833 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