Don't set bogus height on new fragmentainer groups initially.

third_party/WebKit/Source/core/layout/MultiColumnFragmentainerGroup.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 
 #include "core/layout/MultiColumnFragmentainerGroup.h"
 
 #include "core/layout/ColumnBalancer.h"
 #include "core/layout/LayoutMultiColumnSet.h"
@@ skipping 21 matching lines @@
     if (!m_columnSet.flowThread()->isHorizontalWritingMode())
         return offset.transposedSize();
     return offset;
 }
 
 LayoutUnit MultiColumnFragmentainerGroup::blockOffsetInEnclosingFlowThread() const
 {
     return logicalTop() + m_columnSet.logicalTop() + m_columnSet.multiColumnFlowThread()->blockOffsetInEnclosingFlowThread();
 }
 
-bool MultiColumnFragmentainerGroup::heightIsAuto() const
-{
-    // Only the last row may have auto height, and thus be balanced. There are no good reasons to
-    // balance the preceding rows, and that could potentially lead to an insane number of layout
-    // passes as well.
-    return isLastGroup() && m_columnSet.heightIsAuto();
-}
-
 void MultiColumnFragmentainerGroup::resetColumnHeight()
 {
     m_maxColumnHeight = calculateMaxColumnHeight();
 
     LayoutMultiColumnFlowThread* flowThread = m_columnSet.multiColumnFlowThread();
-    if (heightIsAuto()) {
+    if (m_columnSet.heightIsAuto()) {
         LayoutMultiColumnFlowThread* enclosingFlowThread = flowThread->enclosingFlowThread();
         if (enclosingFlowThread && enclosingFlowThread->isPageLogicalHeightKnown()) {
             // Even if height is auto, we set an initial height, in order to tell how much content
             // this MultiColumnFragmentainerGroup can hold, and when we need to append a new one.
             m_columnHeight = m_maxColumnHeight;
         } else {
             m_columnHeight = LayoutUnit();
         }
     } else {
         setAndConstrainColumnHeight(heightAdjustedForRowOffset(flowThread->columnHeightAvailable()));
     }
 }
 
 bool MultiColumnFragmentainerGroup::recalculateColumnHeight(BalancedColumnHeightCalculation calculationMode)
 {
     LayoutUnit oldColumnHeight = m_columnHeight;
 
     m_maxColumnHeight = calculateMaxColumnHeight();
 
-    if (heightIsAuto()) {
+    // Only the last row may have auto height, and thus be balanced. There are no good reasons to
+    // balance the preceding rows, and that could potentially lead to an insane number of layout
+    // passes as well.
+    if (isLastGroup() && m_columnSet.heightIsAuto()) {
         LayoutUnit newColumnHeight = calculateColumnHeight(calculationMode);
         setAndConstrainColumnHeight(newColumnHeight);
         // After having calculated an initial column height, the multicol container typically needs at
         // least one more layout pass with a new column height, but if a height was specified, we only
         // need to do this if we think that we need less space than specified. Conversely, if we
         // determined that the columns need to be as tall as the specified height of the container, we
         // have already laid it out correctly, and there's no need for another pass.
     } else {
         // The position of the column set may have changed, in which case height available for
         // columns may have changed as well.
@@ skipping 468 matching lines @@
     append(MultiColumnFragmentainerGroup(m_columnSet));
     return last();
 }
 
 void MultiColumnFragmentainerGroupList::deleteExtraGroups()
 {
     shrink(1);
 }
 
 } // namespace blink