Auto merge of #17839 - heycam:opacity-smil, r=hiro

style: allow out-of-range opacity values for SMIL animations

From https://bugzilla.mozilla.org/show_bug.cgi?id=1371150.

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tests/unit/style/parsing/mod.rs

@@ -60,6 +60,7 @@ fn assert_computed_serialization<C, F, T>(f: F, input: &'static str, output: &st
         font_metrics_provider: &ServoMetricsProvider,
         in_media_query: false,
         quirks_mode: QuirksMode::NoQuirks,
+        for_smil_animation: false,
     };
 
     let parsed = parse(f, input).unwrap();