4 files changed, 7 insertions, 11 deletions
diff --git a/components/layout/flow/inline/line.rs b/components/layout/flow/inline/line.rs
index e65eaed2367..80bab1080ed 100644
--- a/components/layout/flow/inline/line.rs
+++ b/components/layout/flow/inline/line.rs
@@ -331,7 +331,7 @@ impl LineItemLayout<'_, '_> {
             self.calculate_inline_box_block_start(inline_box_state, space_above_baseline);
 
         let positioning_context_or_start_offset_in_parent =
-            match inline_box.base.new_positioning_context() {
+            match PositioningContext::new_for_layout_box_base(&inline_box.base) {
                 Some(positioning_context) => Either::Left(positioning_context),
                 None => Either::Right(self.current_positioning_context_mut().len()),
             };
diff --git a/components/layout/flow/inline/mod.rs b/components/layout/flow/inline/mod.rs
index 25fbaa324b1..2023f4e7174 100644
--- a/components/layout/flow/inline/mod.rs
+++ b/components/layout/flow/inline/mod.rs
@@ -2004,9 +2004,7 @@ impl IndependentFormattingContext {
         bidi_level: Level,
     ) {
         // We need to know the inline size of the atomic before deciding whether to do the line break.
-        let mut child_positioning_context = self
-            .new_positioning_context()
-            .unwrap_or_else(|| PositioningContext::new_for_subtree(true));
+        let mut child_positioning_context = PositioningContext::default();
         let IndependentFloatOrAtomicLayoutResult {
             mut fragment,
             baselines,
diff --git a/components/layout/flow/mod.rs b/components/layout/flow/mod.rs
index 983282dc389..0c326c4cc6d 100644
--- a/components/layout/flow/mod.rs
+++ b/components/layout/flow/mod.rs
@@ -689,16 +689,13 @@ fn layout_block_level_children_in_parallel(
     placement_state: &mut PlacementState,
     ignore_block_margins_for_stretch: LogicalSides1D<bool>,
 ) -> Vec<Fragment> {
-    let collects_for_nearest_positioned_ancestor =
-        positioning_context.collects_for_nearest_positioned_ancestor();
     let mut layout_results: Vec<(Fragment, PositioningContext)> =
         Vec::with_capacity(child_boxes.len());
 
     child_boxes
         .par_iter()
         .map(|child_box| {
-            let mut child_positioning_context =
-                PositioningContext::new_for_subtree(collects_for_nearest_positioned_ancestor);
+            let mut child_positioning_context = PositioningContext::default();
             let fragment = child_box.borrow().layout(
                 layout_context,
                 &mut child_positioning_context,
@@ -2241,7 +2238,9 @@ fn block_size_is_zero_or_intrinsic(size: &StyleSize, containing_block: &Containi
             lp.is_definitely_zero() ||
                 (lp.0.has_percentage() && !containing_block.size.block.is_definite())
         },
-        StyleSize::AnchorSizeFunction(_) => unreachable!("anchor-size() should be disabled"),
+        StyleSize::AnchorSizeFunction(_) | StyleSize::AnchorContainingCalcFunction(_) => {
+            unreachable!("anchor-size() should be disabled")
+        },
     }
 }
 
diff --git a/components/layout/flow/root.rs b/components/layout/flow/root.rs
index c6498eeed63..bb9ff1d337a 100644
--- a/components/layout/flow/root.rs
+++ b/components/layout/flow/root.rs
@@ -385,8 +385,7 @@ impl BoxTree {
             style,
         };
 
-        let mut positioning_context =
-            PositioningContext::new_for_containing_block_for_all_descendants();
+        let mut positioning_context = PositioningContext::default();
         let independent_layout = self.root.layout(
             layout_context,
             &mut positioning_context,