Auto merge of #18462 - mrobinson:cleanup-building-state, r=emilio

Do some minor cleanups in display list building

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components/layout/block.rs

@@ -31,6 +31,7 @@ use app_units::{Au, MAX_AU};
 use context::LayoutContext;
 use display_list_builder::{BlockFlowDisplayListBuilding, BorderPaintingMode};
 use display_list_builder::{DisplayListBuildState, EstablishContainingBlock};
+use display_list_builder::StackingContextCollectionState;
 use euclid::{Point2D, Rect, SideOffsets2D, Size2D};
 use floats::{ClearType, FloatKind, Floats, PlacementInfo};
 use flow::{self, BaseFlow, EarlyAbsolutePositionInfo, Flow, FlowClass, ForceNonfloatedFlag};
@@ -1679,7 +1680,7 @@ impl BlockFlow {
         }
     }
 
-    pub fn overflow_style_may_require_scroll_root(&self) -> bool {
+    pub fn overflow_style_may_require_clip_scroll_node(&self) -> bool {
         match (self.fragment.style().get_box().overflow_x,
                self.fragment.style().get_box().overflow_y) {
             (overflow_x::T::auto, _) | (overflow_x::T::scroll, _) | (overflow_x::T::hidden, _) |
@@ -2150,7 +2151,7 @@ impl Flow for BlockFlow {
         }
     }
 
-    fn collect_stacking_contexts(&mut self, state: &mut DisplayListBuildState) {
+    fn collect_stacking_contexts(&mut self, state: &mut StackingContextCollectionState) {
         self.collect_stacking_contexts_for_block(state, EstablishContainingBlock::Yes);
     }