Use a RwLock to cache inline_content_sizes() (#34232)

In order to support size keywords in block layout, we may need to call
`inline_content_sizes()` in order to compute the min/max-content sizes.
But this required a mutable reference in order the update the cache,
and in various places we already had mutable references.

So this switches the cache into a RwLock to avoid needing mutable refs.
Note OnceCell wouldn't work because it's not thread-safe.

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

components/layout_2020/flow/float.rs

@@ -891,7 +891,7 @@ impl FloatBox {
     /// the float containing block formatting context. A later step adjusts the position
     /// to be relative to the containing block.
     pub fn layout(
-        &mut self,
+        &self,
         layout_context: &LayoutContext,
         positioning_context: &mut PositioningContext,
         containing_block: &ContainingBlock,

components/layout_2020/flow/inline/mod.rs

@@ -1656,7 +1656,7 @@ impl InlineFormattingContext {
         }
 
         for item in self.inline_items.iter() {
-            let item = &mut *item.borrow_mut();
+            let item = &*item.borrow();
 
             // Any new box should flush a pending hard line break.
             if !matches!(item, InlineItem::EndInlineBox) {
@@ -1684,7 +1684,7 @@ impl InlineFormattingContext {
                         },
                     ));
                 },
-                InlineItem::OutOfFlowFloatBox(ref mut float_box) => {
+                InlineItem::OutOfFlowFloatBox(ref float_box) => {
                     float_box.layout_into_line_items(&mut layout);
                 },
             }
@@ -1915,7 +1915,7 @@ impl InlineContainerState {
 
 impl IndependentFormattingContext {
     fn layout_into_line_items(
-        &mut self,
+        &self,
         layout: &mut InlineFormattingContextLayout,
         offset_in_text: usize,
         bidi_level: Level,
@@ -2071,7 +2071,7 @@ impl IndependentFormattingContext {
 }
 
 impl FloatBox {
-    fn layout_into_line_items(&mut self, layout: &mut InlineFormattingContextLayout) {
+    fn layout_into_line_items(&self, layout: &mut InlineFormattingContextLayout) {
         let fragment = self.layout(
             layout.layout_context,
             layout.positioning_context,
@@ -2211,7 +2211,7 @@ impl<'layout_data> ContentSizesComputation<'layout_data> {
         inline_formatting_context: &InlineFormattingContext,
     ) -> InlineContentSizesResult {
         for inline_item in inline_formatting_context.inline_items.iter() {
-            self.process_item(&mut inline_item.borrow_mut(), inline_formatting_context);
+            self.process_item(&inline_item.borrow(), inline_formatting_context);
         }
 
         self.forced_line_break();
@@ -2223,7 +2223,7 @@ impl<'layout_data> ContentSizesComputation<'layout_data> {
 
     fn process_item(
         &mut self,
-        inline_item: &mut InlineItem,
+        inline_item: &InlineItem,
         inline_formatting_context: &InlineFormattingContext,
     ) {
         match inline_item {

components/layout_2020/flow/mod.rs

@@ -370,10 +370,10 @@ fn calculate_inline_content_size_for_block_level_boxes(
     containing_block: &IndefiniteContainingBlock,
 ) -> InlineContentSizesResult {
     let get_box_info = |box_: &ArcRefCell<BlockLevelBox>| {
-        match &mut *box_.borrow_mut() {
+        match &*box_.borrow() {
             BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(_) |
             BlockLevelBox::OutsideMarker { .. } => None,
-            BlockLevelBox::OutOfFlowFloatBox(ref mut float_box) => {
+            BlockLevelBox::OutOfFlowFloatBox(ref float_box) => {
                 let inline_content_sizes_result = float_box.contents.outer_inline_content_sizes(
                     layout_context,
                     containing_block,
@@ -404,7 +404,7 @@ fn calculate_inline_content_size_for_block_level_boxes(
                 // Instead, we treat it like an independent block with 'clear: both'.
                 Some((inline_content_sizes_result, Float::None, Clear::Both))
             },
-            BlockLevelBox::Independent(ref mut independent) => {
+            BlockLevelBox::Independent(ref independent) => {
                 let inline_content_sizes_result = independent.outer_inline_content_sizes(
                     layout_context,
                     containing_block,
@@ -606,7 +606,7 @@ fn layout_block_level_children_in_parallel(
         .map(|child_box| {
             let mut child_positioning_context =
                 PositioningContext::new_for_subtree(collects_for_nearest_positioned_ancestor);
-            let fragment = child_box.borrow_mut().layout(
+            let fragment = child_box.borrow().layout(
                 layout_context,
                 &mut child_positioning_context,
                 containing_block,
@@ -646,7 +646,7 @@ fn layout_block_level_children_sequentially(
         .iter()
         .map(|child_box| {
             let positioning_context_length_before_layout = positioning_context.len();
-            let mut fragment = child_box.borrow_mut().layout(
+            let mut fragment = child_box.borrow().layout(
                 layout_context,
                 positioning_context,
                 containing_block,
@@ -670,7 +670,7 @@ fn layout_block_level_children_sequentially(
 
 impl BlockLevelBox {
     fn layout(
-        &mut self,
+        &self,
         layout_context: &LayoutContext,
         positioning_context: &mut PositioningContext,
         containing_block: &ContainingBlock,
@@ -1997,7 +1997,7 @@ fn block_size_is_zero_or_intrinsic(size: &StyleSize, containing_block: &Containi
 
 impl IndependentFormattingContext {
     pub(crate) fn layout_float_or_atomic_inline(
-        &mut self,
+        &self,
         layout_context: &LayoutContext,
         child_positioning_context: &mut PositioningContext,
         containing_block: &ContainingBlock,