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

Source/core/layout/LayoutBlockFlow.cpp

Index: Source/core/layout/LayoutBlockFlow.cpp
diff --git a/Source/core/layout/LayoutBlockFlow.cpp b/Source/core/layout/LayoutBlockFlow.cpp
index 4a61c42bd3e755cbc2d2aee165a938c4d64d2172..92339397838f5d5798dd85b13e38564c4f5a490b 100644
--- a/Source/core/layout/LayoutBlockFlow.cpp
+++ b/Source/core/layout/LayoutBlockFlow.cpp
@@ -209,11 +209,23 @@ bool LayoutBlockFlow::updateLogicalWidthAndColumnWidth()
 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);