Auto merge of #17972 - heycam:ignore-existing, r=bholley

style: Allow styles to be computed ignoring existing element data.

From https://bugzilla.mozilla.org/show_bug.cgi?id=1384824.

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components/style/gecko/generated/bindings.rs

@@ -2827,7 +2827,8 @@ extern "C" {
                                     rule_inclusion: StyleRuleInclusion,
                                     snapshots:
                                         *const ServoElementSnapshotTable,
-                                    set: RawServoStyleSetBorrowed)
+                                    set: RawServoStyleSetBorrowed,
+                                    ignore_existing_styles: bool)
      -> ServoStyleContextStrong;
 }
 extern "C" {