Don't update column position in StyleDidChange.

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

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
@@ skipping 63 matching lines @@
 LayoutTable::~LayoutTable() {}
 
 void LayoutTable::StyleDidChange(StyleDifference diff,
                                  const ComputedStyle* old_style) {
   LayoutBlock::StyleDidChange(diff, old_style);
 
   bool old_fixed_table_layout =
       old_style ? old_style->IsFixedTableLayout() : false;
 
   // In the collapsed border model, there is no cell spacing.
   h_spacing_ = ShouldCollapseBorders() ? 0 : Style()->HorizontalBorderSpacing();

[mstensho (USE GERRIT), 2017/05/04 13:37:52]

Furthermore, why are we updating h_spacing_ and v_spacing_ at this point? Can't
it wait until UpdateLayout()?

[rune, 2017/05/04 20:32:03]

That sounds like a good idea, assuming LayoutTable::UpdateLayout is always
called when the new h/v_border_spacing_ needs to be updated.

   v_spacing_ = ShouldCollapseBorders() ? 0 : Style()->VerticalBorderSpacing();
-  effective_column_positions_[0] = h_spacing_;
 
   if (!table_layout_ ||
       Style()->IsFixedTableLayout() != old_fixed_table_layout) {
     if (table_layout_)
       table_layout_->WillChangeTableLayout();
 
     // According to the CSS2 spec, you only use fixed table layout if an
     // explicit width is specified on the table. Auto width implies auto table
     // layout.
     if (Style()->IsFixedTableLayout())
@@ skipping 1664 matching lines @@
 }
 
 LayoutUnit LayoutTable::PaddingRight() const {
   if (ShouldCollapseBorders())
     return LayoutUnit();
 
   return LayoutBlock::PaddingRight();
 }
 
 }  // namespace blink