layout: Add a InlineFormattingContextBuilder (#32415)

The main change here is that collapsed and `text-transform`'d text is
computed as it's processed by DOM traversal. This single transformed
text is stored in the root of the `InlineFormattingContext`.

This will eventually allow performing linebreaking and shaping of the
entire inline formatting context at once. Allowing for intelligent
processing of linebreaking and also shaping across elements. This
matches more closely what LayoutNG does.

This shouldn't have any (or negligable) behavioral changes, but will
allow us to prevent linebreaking inside of clusters in a followup
change.

Co-authored-by: Rakhi Sharma <atbrakhi@igalia.com>

components/gfx/text/glyph.rs

@@ -440,7 +440,14 @@ pub struct GlyphStore {
 
     /// Used to check if fast path should be used in glyph iteration.
     has_detailed_glyphs: bool,
+
+    /// Whether or not this glyph store contains only glyphs for whitespace.
     is_whitespace: bool,
+
+    /// Whether or not this glyph store contains only a single glyph for a single
+    /// preserved newline.
+    is_single_preserved_newline: bool,
+
     is_rtl: bool,
 }
 
@@ -448,7 +455,12 @@ impl<'a> GlyphStore {
     /// Initializes the glyph store, but doesn't actually shape anything.
     ///
     /// Use the `add_*` methods to store glyph data.
-    pub fn new(length: usize, is_whitespace: bool, is_rtl: bool) -> GlyphStore {
+    pub fn new(
+        length: usize,
+        is_whitespace: bool,
+        is_single_preserved_newline: bool,
+        is_rtl: bool,
+    ) -> GlyphStore {
         assert!(length > 0);
 
         GlyphStore {
@@ -458,6 +470,7 @@ impl<'a> GlyphStore {
             total_word_separators: 0,
             has_detailed_glyphs: false,
             is_whitespace,
+            is_single_preserved_newline,
             is_rtl,
         }
     }
@@ -794,4 +807,9 @@ impl GlyphRun {
             Ordering::Equal
         }
     }
+
+    #[inline]
+    pub fn is_single_preserved_newline(&self) -> bool {
+        self.glyph_store.is_single_preserved_newline
+    }
 }