Auto merge of #16609 - nox:quirks, r=Manishearth,emilio

Implement unitless length quirk

The Gecko side doesn't propagate its quirks mode yet.

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components/style/matching.rs

@@ -483,7 +483,8 @@ trait PrivateMatchMethods: TElement {
                              Some(&mut cascade_info),
                              &*shared_context.error_reporter,
                              font_metrics_provider,
-                             cascade_flags));
+                             cascade_flags,
+                             shared_context.quirks_mode));
 
         cascade_info.finish(&self.as_node());
         values