style: Allow disabling invalidation-based querySelector from C++

Rust compile times are hard.

MozReview-Commit-ID: 9Xhtf7f3Vzv
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>

components/style/dom_apis.rs

@@ -512,11 +512,21 @@ where
     });
 }
 
+/// Whether the invalidation machinery should be used for this query.
+#[derive(PartialEq)]
+pub enum MayUseInvalidation {
+    /// We may use it if we deem it useful.
+    Yes,
+    /// Don't use it.
+    No,
+}
+
 /// <https://dom.spec.whatwg.org/#dom-parentnode-queryselector>
 pub fn query_selector<E, Q>(
     root: E::ConcreteNode,
     selector_list: &SelectorList<E::Impl>,
     results: &mut Q::Output,
+    may_use_invalidation: MayUseInvalidation,
 )
 where
     E: TElement,
@@ -561,6 +571,7 @@ where
     // A selector with a combinator needs to have a length of at least 3: A
     // simple selector, a combinator, and another simple selector.
     let invalidation_may_be_useful =
+        may_use_invalidation == MayUseInvalidation::Yes &&
         selector_list.0.iter().any(|s| s.len() > 2);
 
     if root_element.is_some() || !invalidation_may_be_useful {

ports/geckolib/glue.rs

@@ -1693,17 +1693,27 @@ pub unsafe extern "C" fn Servo_SelectorList_Matches(
 pub unsafe extern "C" fn Servo_SelectorList_QueryFirst(
     node: RawGeckoNodeBorrowed,
     selectors: RawServoSelectorListBorrowed,
+    may_use_invalidation: bool,
 ) -> *const structs::RawGeckoElement {
     use std::borrow::Borrow;
-    use style::dom_apis::{self, QueryFirst};
+    use style::dom_apis::{self, MayUseInvalidation, QueryFirst};
 
     let node = GeckoNode(node);
     let selectors = ::selectors::SelectorList::from_ffi(selectors).borrow();
     let mut result = None;
+
+    let may_use_invalidation =
+        if may_use_invalidation {
+            MayUseInvalidation::Yes
+        } else {
+            MayUseInvalidation::No
+        };
+
     dom_apis::query_selector::<GeckoElement, QueryFirst>(
         node,
         &selectors,
         &mut result,
+        may_use_invalidation,
     );
 
     result.map_or(ptr::null(), |e| e.0)
@@ -1714,19 +1724,28 @@ pub unsafe extern "C" fn Servo_SelectorList_QueryAll(
     node: RawGeckoNodeBorrowed,
     selectors: RawServoSelectorListBorrowed,
     content_list: *mut structs::nsSimpleContentList,
+    may_use_invalidation: bool,
 ) {
     use smallvec::SmallVec;
     use std::borrow::Borrow;
-    use style::dom_apis::{self, QueryAll};
+    use style::dom_apis::{self, MayUseInvalidation, QueryAll};
 
     let node = GeckoNode(node);
     let selectors = ::selectors::SelectorList::from_ffi(selectors).borrow();
     let mut result = SmallVec::new();
 
+    let may_use_invalidation =
+        if may_use_invalidation {
+            MayUseInvalidation::Yes
+        } else {
+            MayUseInvalidation::No
+        };
+
     dom_apis::query_selector::<GeckoElement, QueryAll>(
         node,
         &selectors,
         &mut result,
+        may_use_invalidation,
     );
 
     if !result.is_empty() {