layout: Share styles to inline box children via `SharedInlineStyles` (#36896)

`TextRun`s use their parent style to render. Previously, these styles
were cloned and stored directly in the box tree `TextRun` and resulting
`TextFragment`s. This presents a problem for incremental layout.
Wrapping the style in another layer of shared ownership and mutability
will allow updating all `TextFragment`s during repaint-only incremental
layout by simply updating the box tree styles of the original text
parents.

This adds a new set of borrows when accessing text styles, but also
makes it so that during box tree block construction
`InlineFormattingContext`s are created lazily and now
`InlineFormattingContextBuilder::finish` consumes the builder, making
the API make a bit more sense. This should also improve performance of
box tree block construction slightly.

Testing: This should not change observable behavior and thus is covered
by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/components/layout/construct_modern.rs b/components/layout/construct_modern.rs
index 1489d82635b..8f1282ec9f6 100644
--- a/components/layout/construct_modern.rs
+++ b/components/layout/construct_modern.rs
@@ -142,7 +142,7 @@ impl<'a, 'dom> ModernContainerBuilder<'a, 'dom> {
             .filter_map(|job| match job {
                 ModernContainerJob::TextRuns(runs) => {
                     let mut inline_formatting_context_builder =
-                        InlineFormattingContextBuilder::new();
+                        InlineFormattingContextBuilder::new(self.info);
                     for flex_text_run in runs.into_iter() {
                         inline_formatting_context_builder
                             .push_text(flex_text_run.text, &flex_text_run.info);