Don't always invalidate collapsed borders during table layout

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 84 matching lines @@
     // layout.
     if (Style()->IsFixedTableLayout())
       table_layout_ = WTF::MakeUnique<TableLayoutAlgorithmFixed>(this);
     else
       table_layout_ = WTF::MakeUnique<TableLayoutAlgorithmAuto>(this);
   }
 
   if (!old_style)
     return;
 
-  LayoutTableBoxComponent::InvalidateCollapsedBordersOnStyleChange(
-      *this, *this, diff, *old_style);
+  if (old_style->BorderCollapse() != StyleRef().BorderCollapse()) {
+    InvalidateCollapsedBorders();
+  } else {
+    LayoutTableBoxComponent::InvalidateCollapsedBordersOnStyleChange(
+        *this, *this, diff, *old_style);
+  }
 
   if (LayoutTableBoxComponent::DoCellsHaveDirtyWidth(*this, *this, diff,
                                                      *old_style))
     MarkAllCellsWidthsDirtyAndOrNeedsLayout(kMarkDirtyAndNeedsLayout);
 }
 
 static inline void ResetSectionPointerIfNotBefore(LayoutTableSection*& ptr,
                                                   LayoutObject* before) {
   if (!before || !ptr)
     return;
@@ skipping 632 matching lines @@
 
     UpdateLogicalHeight();
 
     // table can be containing block of positioned elements.
     bool dimension_changed = old_logical_width != LogicalWidth() ||
                              old_logical_height != LogicalHeight();
     LayoutPositionedObjects(dimension_changed);
 
     UpdateLayerTransformAfterLayout();
 
-    // Layout was changed, so probably borders too.
-    InvalidateCollapsedBorders();
-
     ComputeOverflow(ClientLogicalBottom());
     UpdateAfterLayout();
 
     if (state.IsPaginated() && IsPageLogicalHeightKnown()) {
       block_offset_to_first_repeatable_header_ = state.PageLogicalOffset(
           *this, top_section ? top_section->LogicalTop() : LayoutUnit());
     }
   }
 
   // FIXME: This value isn't the intrinsic content logical height, but we need
   // to update the value as its used by flexbox layout. crbug.com/367324
   SetIntrinsicContentLogicalHeight(ContentLogicalHeight());
 
   column_logical_width_changed_ = false;
   ClearNeedsLayout();
 }
 
 void LayoutTable::InvalidateCollapsedBorders() {
   collapsed_borders_.clear();
-  if (!CollapseBorders())
-    return;
-
   collapsed_borders_valid_ = false;
   SetMayNeedPaintInvalidation();
 }
 
 // Collect all the unique border values that we want to paint in a sorted list.
 // During the collection, each cell saves its recalculated borders into the
 // cache of its containing section, and invalidates itself if any border
 // changes. This method doesn't affect layout.
 void LayoutTable::RecalcCollapsedBordersIfNeeded() {
   if (collapsed_borders_valid_ || !CollapseBorders())
@@ skipping 946 matching lines @@
 }
 
 LayoutUnit LayoutTable::PaddingRight() const {
   if (CollapseBorders())
     return LayoutUnit();
 
   return LayoutBlock::PaddingRight();
 }
 
 }  // namespace blink