layout: Make IndependentFormattingContext::contents private (again) (#38350)

This was done in #24871, but after some refactorings it became public.
This makes it private again. As said in
b2b3ea992c:

> Privacy forces the rest of the code to go through methods
> rather than matching on the enum,
> reducing accidental layout-mode-specific behavior.

It also avoids the risk of accidentally calling `layout()` on the inner
layout-mode-specific struct, bypassing caching.

Testing: Not needed (no behavior change)

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

components/layout/flow/inline/mod.rs

@@ -114,10 +114,7 @@ use webrender_api::FontInstanceKey;
 use xi_unicode::linebreak_property;
 
 use super::float::{Clear, PlacementAmongFloats};
-use super::{
-    CacheableLayoutResult, IndependentFloatOrAtomicLayoutResult,
-    IndependentFormattingContextContents,
-};
+use super::{CacheableLayoutResult, IndependentFloatOrAtomicLayoutResult};
 use crate::cell::ArcRefCell;
 use crate::context::LayoutContext;
 use crate::dom_traversal::NodeAndStyleInfo;
@@ -2151,10 +2148,8 @@ impl IndependentFormattingContext {
         match self.style().clone_baseline_source() {
             BaselineSource::First => baselines.first,
             BaselineSource::Last => baselines.last,
-            BaselineSource::Auto => match &self.contents {
-                IndependentFormattingContextContents::Flow(_) => baselines.last,
-                _ => baselines.first,
-            },
+            BaselineSource::Auto if self.is_block_container() => baselines.last,
+            BaselineSource::Auto => baselines.first,
         }
     }
 

components/layout/flow/mod.rs

@@ -28,9 +28,7 @@ use crate::flow::float::{
     Clear, ContainingBlockPositionInfo, FloatBox, FloatSide, PlacementAmongFloats,
     SequentialLayoutState,
 };
-use crate::formatting_contexts::{
-    Baselines, IndependentFormattingContext, IndependentFormattingContextContents,
-};
+use crate::formatting_contexts::{Baselines, IndependentFormattingContext};
 use crate::fragment_tree::{
     BaseFragmentInfo, BlockLevelLayoutInfo, BoxFragment, CollapsedBlockMargins, CollapsedMargin,
     Fragment, FragmentFlags,