Setting -webkit-column-count to auto is the same as not setting it.

Source/core/style/ComputedStyle.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
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     void setWordBreak(EWordBreak b) { SET_VAR(rareInheritedData, wordBreak, b); }
     void setOverflowWrap(EOverflowWrap b) { SET_VAR(rareInheritedData, overflowWrap, b); }
     void setLineBreak(LineBreak b) { SET_VAR(rareInheritedData, lineBreak, b); }
     void setHighlight(const AtomicString& h) { SET_VAR(rareInheritedData, highlight, h); }
     void setHyphenationString(const AtomicString& h) { SET_VAR(rareInheritedData, hyphenationString, h); }
     void setLocale(const AtomicString& locale) { SET_VAR(rareInheritedData, locale, locale); }
     void setResize(EResize r) { SET_VAR(rareNonInheritedData, m_resize, r); }
     void setColumnWidth(float f) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_autoWidth, false); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_width, f); }
     void setHasAutoColumnWidth() { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_autoWidth, true); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_width, 0); }
     void setColumnCount(unsigned short c) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_autoCount, false); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_count, c); }
-    void setHasAutoColumnCount() { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_autoCount, true); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_count, 0); }
+    void setHasAutoColumnCount() { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_autoCount, true); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_count, initialColumnCount()); }
     void setColumnFill(ColumnFill columnFill) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_fill, columnFill); }
     void setColumnGap(float f) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_normalGap, false); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_gap, f); }
     void setHasNormalColumnGap() { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_normalGap, true); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_gap, 0); }
     void setColumnRuleColor(const StyleColor& c) { SET_BORDERVALUE_COLOR(rareNonInheritedData.access()->m_multiCol, m_rule, c); }
     void setColumnRuleStyle(EBorderStyle b) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_rule.m_style, b); }
     void setColumnRuleWidth(unsigned short w) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_rule.m_width, w); }
     void setColumnSpan(ColumnSpan columnSpan) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_columnSpan, columnSpan); }
     void setColumnBreakBefore(EPageBreak p) { SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakBefore, p); }
     // For valid values of column-break-inside see http://www.w3.org/TR/css3-multicol/#break-before-break-after-break-inside
     void setColumnBreakInside(EPageBreak p) { ASSERT(p == PBAUTO || p == PBAVOID); SET_VAR(rareNonInheritedData.access()->m_multiCol, m_breakInside, p); }
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 }
 
 inline bool ComputedStyle::hasPseudoElementStyle() const
 {
     return noninherited_flags.pseudoBits & PSEUDO_ELEMENT_MASK;
 }
 
 } // namespace blink
 
 #endif // ComputedStyle_h