Add integrity checks of flags for NGPhysicalBoxFragment

This patch adds integrity checks for the flags of
|NGPhysicalBoxFragment| and its actual children.

Bug: 982194
Change-Id: Ic18f088c1263d4f76f03dc1f22a88d3700254b68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2050151Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741743}

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

@@ -112,6 +112,10 @@ NGPhysicalBoxFragment::NGPhysicalBoxFragment(
     has_baseline_ = false;
     baseline_ = LayoutUnit::Min();
   }
+
+#if DCHECK_IS_ON()
+  CheckIntegrity();
+#endif
 }
 
 scoped_refptr<const NGLayoutResult>
@@ -490,6 +494,58 @@ void NGPhysicalBoxFragment::CheckSameForSimplifiedLayout(
   DCHECK(Borders() == other.Borders());
   DCHECK(Padding() == other.Padding());
 }
+
+// Check our flags represent the actual children correctly.
+void NGPhysicalBoxFragment::CheckIntegrity() const {
+  bool has_inflow_blocks = false;
+  bool has_inlines = false;
+  bool has_line_boxes = false;
+  bool has_floats = false;
+  bool has_list_markers = false;
+
+  for (const NGLink& child : Children()) {
+    if (child->IsFloating())
+      has_floats = true;
+    else if (child->IsOutOfFlowPositioned())
+      ;  // OOF can be in the fragment tree regardless of |HasItems|.
+    else if (child->IsLineBox())
+      has_line_boxes = true;
+    else if (child->IsListMarker())
+      has_list_markers = true;
+    else if (child->IsInline())
+      has_inlines = true;
+    else
+      has_inflow_blocks = true;
+  }
+
+  // If we have line boxes, |IsInlineFormattingContext()| is true, but the
+  // reverse is not always true.
+  if (has_line_boxes || has_inlines)
+    DCHECK(IsInlineFormattingContext());
+
+  // If display-locked, we may not have any children.
+  DCHECK(layout_object_);
+  if (layout_object_ && layout_object_->PaintBlockedByDisplayLock(
+                            DisplayLockLifecycleTarget::kChildren))
+    return;
+
+  if (RuntimeEnabledFeatures::LayoutNGFragmentItemEnabled()) {
+    if (RuntimeEnabledFeatures::LayoutNGBlockFragmentationEnabled()) {
+      if (has_line_boxes)
+        DCHECK(HasItems());
+    } else {
+      DCHECK_EQ(HasItems(), has_line_boxes);
+    }
+
+    if (has_line_boxes) {
+      DCHECK(!has_inlines);
+      DCHECK(!has_inflow_blocks);
+      // Following objects should be in the items, not in the tree.
+      DCHECK(!has_floats);
+      DCHECK(!has_list_markers);
+    }
+  }
+}
 #endif
 
 }  // namespace blink

third_party/blink/renderer/core/layout/ng/ng_physical_box_fragment.h

@@ -159,6 +159,10 @@ class CORE_EXPORT NGPhysicalBoxFragment final
     return has_borders_ ? address + 1 : address;
   }
 
+#if DCHECK_IS_ON()
+  void CheckIntegrity() const;
+#endif
+
   LayoutUnit baseline_;
   NGLink children_[];
   // borders and padding come from after |children_| if they are not zero.