Optimize collapsed border calculation (step 2)

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

Index: third_party/WebKit/Source/core/layout/LayoutTableRow.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTableRow.cpp b/third_party/WebKit/Source/core/layout/LayoutTableRow.cpp
index b18c797e6ed844e346b6d23b586ab4efcc5706b2..98063f238fce64a43f6f32a8f3df60f225abc7ec 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTableRow.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTableRow.cpp
@@ -71,11 +71,15 @@ void LayoutTableRow::StyleDidChange(StyleDifference diff,
   if (!table)
     return;
 
-  LayoutTableBoxComponent::InvalidateCollapsedBordersOnStyleChange(
-      *this, *table, diff, *old_style);
+  if (LayoutTableBoxComponent::NeedsInvalidateCollapsedBordersOnStyleChange(
+          *this, *table, diff, *old_style))
+    InvalidateCollapsedBordersOfAffectedCells();
 
   if (LayoutTableBoxComponent::DoCellsHaveDirtyWidth(*this, *table, diff,
                                                      *old_style)) {
+    // TODO(wangxianzhu,dgrogan): The following seems incorrect the row's border
+    // is used by cells not in this row. Could reuse some code in
+    // InvalidateCollapsedBordersOfAffectedCells().
     // If the border width changes on a row, we need to make sure the cells in
     // the row know to lay out again.
     // This only happens when borders are collapsed, since they end up affecting
@@ -166,24 +170,31 @@ void LayoutTableRow::AddChild(LayoutObject* child, LayoutObject* before_child) {
 
   // Generated content can result in us having a null section so make sure to
   // null check our parent.
-  if (Parent()) {
-    Section()->AddCell(cell, this);
-    // When borders collapse, adding a cell can affect the the width of
-    // neighboring cells.
-    LayoutTable* enclosing_table = Table();
-    if (enclosing_table && enclosing_table->CollapseBorders()) {
-      enclosing_table->InvalidateCollapsedBorders();
-      if (LayoutTableCell* previous_cell = cell->PreviousCell())
-        previous_cell->SetNeedsLayoutAndPrefWidthsRecalc(
-            LayoutInvalidationReason::kTableChanged);
-      if (LayoutTableCell* next_cell = cell->NextCell())
-        next_cell->SetNeedsLayoutAndPrefWidthsRecalc(
-            LayoutInvalidationReason::kTableChanged);
-    }
-  }
+  if (!Parent())
+    return;
+
+  Section()->AddCell(cell, this);
 
   if (before_child || NextRow())
     Section()->SetNeedsCellRecalc();
+
+  // When borders collapse, adding a cell can affect the the width of
+  // neighboring cells.
+  LayoutTable* enclosing_table = Table();
+  if (enclosing_table && enclosing_table->CollapseBorders()) {
+    cell->InvalidateCollapsedBordersOfAffectedCells();
+    // TODO(wangxianzhu,dgrogan): The following seems incorrect if the cell has
+    // adjacent cells other than PreviousCell() and NextCell(). Could reuse some
+    // code in LayoutTableCell::InvalidateCollapsedBordersOfAffectedCells().
+    if (LayoutTableCell* previous_cell = cell->PreviousCell()) {
+      previous_cell->SetNeedsLayoutAndPrefWidthsRecalc(
+          LayoutInvalidationReason::kTableChanged);
+    }
+    if (LayoutTableCell* next_cell = cell->NextCell()) {
+      next_cell->SetNeedsLayoutAndPrefWidthsRecalc(
+          LayoutInvalidationReason::kTableChanged);
+    }
+  }
 }
 
 void LayoutTableRow::UpdateLayout() {
@@ -333,4 +344,35 @@ bool LayoutTableRow::IsFirstRowInSectionAfterHeader() const {
          header->GetPaginationBreakability() != kAllowAnyBreaks;
 }
 
+void LayoutTableRow::InvalidateCollapsedBordersOfAffectedCells() {
+  auto* table = Table();
+  DCHECK(table->CollapseBorders());
+  if (table->NeedsInvalidateCollapsedBordersForAllCells())
+    return;
+
+  table->RecalcSectionsIfNeeded();
+  table->InvalidateCollapsedBorders();
+
+  // Invalidate cells intersecting this row.
+  auto* section = Section();
+  section->InvalidateCellCollapsedBordersIntersectingRow(RowIndex());
+
+  // Invalidate cells above this row.
+  if (RowIndex()) {
+    section->InvalidateCellCollapsedBordersIntersectingRow(RowIndex() - 1);
+  } else if (auto* section_above =
+                 table->SectionAbove(section, kSkipEmptySections)) {
+    section_above->InvalidateCellCollapsedBordersIntersectingRow(
+        section_above->NumRows() - 1);
+  }
+
+  // Invalidate cells below this row.
+  if (RowIndex() + 1 < section->NumRows()) {
+    section->InvalidateCellCollapsedBordersIntersectingRow(RowIndex() + 1);
+  } else if (auto* section_below =
+                 table->SectionBelow(section, kSkipEmptySections)) {
+    section_below->InvalidateCellCollapsedBordersIntersectingRow(0);
+  }
+}
+
 }  // namespace blink