style: Look at the snapshots when invalidating due to stylesheet changes.

Otherwise removal of stylesheets may get out of sync with other DOM changes, and
we may fail to invalidate the style of the affected elements.

Bug: 1432850
Reviewed-by: bz
MozReview-Commit-ID: DrMTgLzQcnk

components/style/invalidation/element/element_wrapper.rs

@@ -71,7 +71,8 @@ pub struct ElementWrapper<'a, E>
 }
 
 impl<'a, E> ElementWrapper<'a, E>
-    where E: TElement,
+where
+    E: TElement,
 {
     /// Trivially constructs an `ElementWrapper`.
     pub fn new(el: E, snapshot_map: &'a SnapshotMap) -> Self {