[New Multicolumn] Give up on stretching columns if they have already reached max height.

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/LayoutMultiColumnSet.h"
 
@@ skipping 402 matching lines @@
         // With the current column height, the content fits without creating overflowing columns. We're done.
         return m_columnHeight;
     }
 
     if (m_contentRuns.size() >= m_columnSet.usedColumnCount()) {
         // Too many forced breaks to allow any implicit breaks. Initial balancing should already
         // have set a good height. There's nothing more we should do.
         return m_columnHeight;
     }
 
+    if (m_columnHeight >= m_maxColumnHeight) {
+        // We cannot stretch any further. We'll just have to live with the overflowing columns. This
+        // typically happens if the max column height is less than the height of the tallest piece
+        // of unbreakable content (e.g. lines).
+        return m_columnHeight;
+    }
+
     // If the initial guessed column height wasn't enough, stretch it now. Stretch by the lowest
     // amount of space shortage found during layout.
 
     ASSERT(m_minSpaceShortage > 0); // We should never _shrink_ the height!
     ASSERT(m_minSpaceShortage != LayoutFlowThread::maxLogicalHeight()); // If this happens, we probably have a bug.
     if (m_minSpaceShortage == LayoutFlowThread::maxLogicalHeight())
         return m_columnHeight; // So bail out rather than looping infinitely.
 
     return m_columnHeight + m_minSpaceShortage;
 }
@@ skipping 113 matching lines @@
     append(MultiColumnFragmentainerGroup(m_columnSet));
     return last();
 }
 
 void MultiColumnFragmentainerGroupList::deleteExtraGroups()
 {
     shrink(1);
 }
 
 } // namespace blink