1 files changed, 55 insertions, 8 deletions

diff --git a/chromium/third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.cc b/chromium/third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.cc
index cf4cd3d83c4..c564536a860 100644
--- a/chromium/third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.cc
+++ b/chromium/third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.cc
@@ -4,6 +4,7 @@
 
 #include "third_party/blink/renderer/core/layout/ng/layout_ng_fieldset.h"
 
+#include "third_party/blink/renderer/core/dom/layout_tree_builder_traversal.h"
 #include "third_party/blink/renderer/core/layout/layout_fieldset.h"
 #include "third_party/blink/renderer/core/layout/layout_object_factory.h"
 
@@ -14,9 +15,50 @@ LayoutNGFieldset::LayoutNGFieldset(Element* element)
   SetChildrenInline(false);
 }
 
+LayoutBlock* LayoutNGFieldset::FindAnonymousFieldsetContentBox() const {
+  LayoutObject* first_child = FirstChild();
+  if (!first_child)
+    return nullptr;
+  if (first_child->IsAnonymous())
+    return To<LayoutBlock>(first_child);
+  LayoutObject* last_child = first_child->NextSibling();
+  DCHECK(!last_child || !last_child->NextSibling());
+  if (last_child && last_child->IsAnonymous())
+    return To<LayoutBlock>(last_child);
+  return nullptr;
+}
+
 void LayoutNGFieldset::AddChild(LayoutObject* new_child,
                                 LayoutObject* before_child) {
-  LayoutBlock* fieldset_content = To<LayoutBlock>(FirstChild());
+  if (!new_child->IsText()) {
+    // Adding a child LayoutObject always causes reattach of <fieldset>. So
+    // |before_child| is always nullptr.
+    // See HTMLFieldSetElement::DidRecalcStyle().
+    DCHECK(!before_child);
+  } else if (before_child && before_child->IsRenderedLegend()) {
+    // Whitespace changes resulting from removed nodes are handled in
+    // MarkForWhitespaceReattachment(), and don't trigger
+    // HTMLFieldSetElement::DidRecalcStyle(). So the fieldset is not
+    // reattached. We adjust |before_child| instead.
+    Node* before_node =
+        LayoutTreeBuilderTraversal::NextLayoutSibling(*before_child->GetNode());
+    before_child = before_node ? before_node->GetLayoutObject() : nullptr;
+  }
+
+  // https://html.spec.whatwg.org/C/#the-fieldset-and-legend-elements
+  // > * If the element has a rendered legend, then that element is expected
+  // >   to be the first child box.
+  // > * The anonymous fieldset content box is expected to appear after the
+  // >   rendered legend and is expected to contain the content (including
+  // >   the '::before' and '::after' pseudo-elements) of the fieldset
+  // >   element except for the rendered legend, if there is one.
+
+  if (new_child->IsRenderedLegendCandidate() &&
+      !LayoutFieldset::FindInFlowLegend(*this)) {
+    LayoutNGBlockFlow::AddChild(new_child, FirstChild());
+    return;
+  }
+  LayoutBlock* fieldset_content = FindAnonymousFieldsetContentBox();
   if (!fieldset_content) {
     // We wrap everything inside an anonymous child, which will take care of the
     // fieldset contents. This parent will only be responsible for the fieldset
@@ -76,7 +118,7 @@ void LayoutNGFieldset::UpdateAnonymousChildStyle(
   child_style.SetPaddingBottom(StyleRef().PaddingBottom());
   child_style.SetPaddingLeft(StyleRef().PaddingLeft());
 
-  if (StyleRef().SpecifiesColumns()) {
+  if (StyleRef().SpecifiesColumns() && AllowsColumns()) {
     child_style.SetColumnCount(StyleRef().ColumnCount());
     child_style.SetColumnWidth(StyleRef().ColumnWidth());
   } else {
@@ -100,12 +142,19 @@ void LayoutNGFieldset::UpdateAnonymousChildStyle(
   child_style.SetGridColumnStart(StyleRef().GridColumnStart());
   child_style.SetGridRowEnd(StyleRef().GridRowEnd());
   child_style.SetGridRowStart(StyleRef().GridRowStart());
+
+  // grid-template-columns, grid-template-rows
   child_style.SetGridTemplateColumns(StyleRef().GridTemplateColumns());
   child_style.SetGridTemplateRows(StyleRef().GridTemplateRows());
   child_style.SetNamedGridArea(StyleRef().NamedGridArea());
   child_style.SetNamedGridAreaColumnCount(
       StyleRef().NamedGridAreaColumnCount());
   child_style.SetNamedGridAreaRowCount(StyleRef().NamedGridAreaRowCount());
+  child_style.SetImplicitNamedGridColumnLines(
+      StyleRef().ImplicitNamedGridColumnLines());
+  child_style.SetImplicitNamedGridRowLines(
+      StyleRef().ImplicitNamedGridRowLines());
+
   child_style.SetRowGap(StyleRef().RowGap());
 
   child_style.SetJustifyContent(StyleRef().JustifyContent());
@@ -171,16 +220,14 @@ bool LayoutNGFieldset::HitTestChildren(HitTestResult& result,
 }
 
 LayoutUnit LayoutNGFieldset::ScrollWidth() const {
-  const LayoutObject* child = FirstChild();
-  if (child && child->IsAnonymous())
-    return To<LayoutBox>(child)->ScrollWidth();
+  if (const auto* content = FindAnonymousFieldsetContentBox())
+    return content->ScrollWidth();
   return LayoutNGBlockFlow::ScrollWidth();
 }
 
 LayoutUnit LayoutNGFieldset::ScrollHeight() const {
-  const LayoutObject* child = FirstChild();
-  if (child && child->IsAnonymous())
-    return To<LayoutBox>(child)->ScrollHeight();
+  if (const auto* content = FindAnonymousFieldsetContentBox())
+    return content->ScrollHeight();
   return LayoutNGBlockFlow::ScrollHeight();
 }