Merging upstream version 127.0.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 23 insertions, 7 deletions

diff --git a/servo/components/style/data.rs b/servo/components/style/data.rs
index ceddc5bd20..366318b658 100644
--- a/servo/components/style/data.rs
+++ b/servo/components/style/data.rs
@@ -45,6 +45,9 @@ bitflags! {
         /// The former gives us stronger transitive guarantees that allows us to
         /// apply the style sharing cache to cousins.
         const PRIMARY_STYLE_REUSED_VIA_RULE_NODE = 1 << 2;
+
+        /// Whether this element may have matched rules inside @starting-style.
+        const MAY_HAVE_STARTING_STYLE = 1 << 3;
     }
 }
 
@@ -344,22 +347,28 @@ impl ElementData {
         let reused_via_rule_node = self
             .flags
             .contains(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE);
+        let may_have_starting_style = self
+            .flags
+            .contains(ElementDataFlags::MAY_HAVE_STARTING_STYLE);
 
         PrimaryStyle {
             style: ResolvedStyle(self.styles.primary().clone()),
             reused_via_rule_node,
+            may_have_starting_style,
         }
     }
 
     /// Sets a new set of styles, returning the old ones.
     pub fn set_styles(&mut self, new_styles: ResolvedElementStyles) -> ElementStyles {
-        if new_styles.primary.reused_via_rule_node {
-            self.flags
-                .insert(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE);
-        } else {
-            self.flags
-                .remove(ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE);
-        }
+        self.flags.set(
+            ElementDataFlags::PRIMARY_STYLE_REUSED_VIA_RULE_NODE,
+            new_styles.primary.reused_via_rule_node,
+        );
+        self.flags.set(
+            ElementDataFlags::MAY_HAVE_STARTING_STYLE,
+            new_styles.primary.may_have_starting_style,
+        );
+
         mem::replace(&mut self.styles, new_styles.into())
     }
 
@@ -542,4 +551,11 @@ impl ElementData {
 
         n
     }
+
+    /// Returns true if this element data may need to compute the starting style for CSS
+    /// transitions.
+    #[inline]
+    pub fn may_have_starting_style(&self) -> bool {
+        self.flags.contains(ElementDataFlags::MAY_HAVE_STARTING_STYLE)
+    }
 }