style: More container queries plumbing

Provide container information in computed::Context and use it to resolve
the container queries.

This still fails a lot of tests because we are not ensuring that layout
is up-to-date when we style the container descendants, but that's
expected.

Differential Revision: https://phabricator.services.mozilla.com/D146478

components/style/queries/condition.rs

@@ -7,7 +7,7 @@
 //! https://drafts.csswg.org/mediaqueries-4/#typedef-media-condition
 //! https://drafts.csswg.org/css-contain-3/#typedef-container-condition
 
-use super::{QueryFeatureExpression, FeatureType};
+use super::{QueryFeatureExpression, FeatureType, FeatureFlags};
 use crate::parser::ParserContext;
 use crate::values::computed;
 use cssparser::{Parser, Token};
@@ -85,6 +85,35 @@ impl QueryCondition {
         Self::parse_internal(context, input, feature_type, AllowOr::Yes)
     }
 
+    fn visit<F>(&self, visitor: &mut F)
+    where
+        F: FnMut(&Self),
+    {
+        visitor(self);
+        match *self {
+            Self::Feature(..) => {},
+            Self::Not(ref cond) => cond.visit(visitor),
+            Self::Operation(ref conds, _op) => {
+                for cond in conds.iter() {
+                    cond.visit(visitor);
+                }
+            },
+            Self::InParens(ref cond) => cond.visit(visitor),
+        }
+    }
+
+    /// Returns the union of all flags in the expression. This is useful for
+    /// container queries.
+    pub fn cumulative_flags(&self) -> FeatureFlags {
+        let mut result = FeatureFlags::empty();
+        self.visit(&mut |condition| {
+            if let Self::Feature(ref f) = condition {
+                result.insert(f.feature_flags())
+            }
+        });
+        result
+    }
+
     /// Parse a single condition, disallowing `or` expressions.
     ///
     /// To be used from the legacy query syntax.