Add NGFragmentItem::IsBlockFormattingContextRoot

This is a follow up for r749120 crrev.com/c/2089894

This patch has no behavior changes.

Bug: 982194
Change-Id: I18775e577dae67b90e98ecddb5b28babca1175e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2098165Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#749590}

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.cc

@@ -38,6 +38,7 @@ NGFragmentItem::NGFragmentItem(const NGPhysicalTextFragment& text)
     // |generated_text_.text_| instead copying, |generated_text_.text = ...|.
     new (&generated_text_.text) String(text.Text().ToString());
   }
+  DCHECK(!IsBlockFormattingContextRoot());
 }
 
 NGFragmentItem::NGFragmentItem(const NGPhysicalLineBoxFragment& line,
@@ -50,7 +51,9 @@ NGFragmentItem::NGFragmentItem(const NGPhysicalLineBoxFragment& line,
       style_variant_(static_cast<unsigned>(line.StyleVariant())),
       is_hidden_for_paint_(false),
       text_direction_(static_cast<unsigned>(line.BaseDirection())),
-      ink_overflow_computed_(false) {}
+      ink_overflow_computed_(false) {
+  DCHECK(!IsBlockFormattingContextRoot());
+}
 
 NGFragmentItem::NGFragmentItem(const NGPhysicalBoxFragment& box,
                                TextDirection resolved_direction)
@@ -61,7 +64,9 @@ NGFragmentItem::NGFragmentItem(const NGPhysicalBoxFragment& box,
       style_variant_(static_cast<unsigned>(box.StyleVariant())),
       is_hidden_for_paint_(box.IsHiddenForPaint()),
       text_direction_(static_cast<unsigned>(resolved_direction)),
-      ink_overflow_computed_(false) {}
+      ink_overflow_computed_(false) {
+  DCHECK_EQ(IsBlockFormattingContextRoot(), box.IsBlockFormattingContextRoot());
+}
 
 NGFragmentItem::NGFragmentItem(const NGInlineItem& inline_item,
                                const PhysicalSize& size)
@@ -76,6 +81,7 @@ NGFragmentItem::NGFragmentItem(const NGInlineItem& inline_item,
   DCHECK_EQ(inline_item.Type(), NGInlineItem::kOpenTag);
   DCHECK(layout_object_);
   DCHECK(layout_object_->IsLayoutInline());
+  DCHECK(!IsBlockFormattingContextRoot());
 }
 
 NGFragmentItem::~NGFragmentItem() {

third_party/blink/renderer/core/layout/ng/inline/ng_fragment_item.h

@@ -260,6 +260,10 @@ class CORE_EXPORT NGFragmentItem : public DisplayItemClient {
     return TextType() == NGTextType::kSymbolMarker;
   }
 
+  bool IsBlockFormattingContextRoot() const {
+    return BoxFragment() && !IsInlineBox();
+  }
+
   const ShapeResultView* TextShapeResult() const;
   NGTextOffset TextOffset() const;
   unsigned StartOffset() const { return TextOffset().start; }

third_party/blink/renderer/core/layout/ng/ng_fragment_child_iterator.cc

@@ -34,7 +34,7 @@ NGFragmentChildIterator NGFragmentChildIterator::Descend() const {
     const NGFragmentItem* item = current_.cursor_->CurrentItem();
     // Descend using the cursor if the current item doesn't establish a new
     // formatting context.
-    if (!item->BoxFragment() || item->IsInlineBox())
+    if (!item->IsBlockFormattingContextRoot())
       return NGFragmentChildIterator(*current_.cursor_);
   }
   DCHECK(current_.BoxFragment());