[threaded-animation-resolution] explicitly obtain ref-counted propert…

…ies as references when blending

https://bugs.webkit.org/show_bug.cgi?id=270455

Reviewed by Dean Jackson.

Several properties of `AcceleratedEffectValues` are ref-counted and we access those when blending in `AcceleratedEffect`.
We don't currently mark those as references, so we should make it explicit since we don't want to increase the ref-counting.

* Source/WebCore/platform/animation/AcceleratedEffect.cpp:
(WebCore::blend):

Canonical link: https://commits.webkit.org/275704@main

Source/WebCore/platform/animation/AcceleratedEffect.cpp

@@ -307,15 +307,15 @@ static void blend(AcceleratedEffectProperty property, AcceleratedEffectValues& o
         break;
     }
     case AcceleratedEffectProperty::Translate:
-        if (auto toTranslate = to.translate)
+        if (auto& toTranslate = to.translate)
             output.translate = toTranslate->blend(from.translate.get(), blendingContext);
         break;
     case AcceleratedEffectProperty::Rotate:
-        if (auto toRotate = to.rotate)
+        if (auto& toRotate = to.rotate)
             output.rotate = toRotate->blend(from.rotate.get(), blendingContext);
         break;
     case AcceleratedEffectProperty::Scale:
-        if (auto toScale = to.scale)
+        if (auto& toScale = to.scale)
             output.scale = toScale->blend(from.scale.get(), blendingContext);
         break;
     case AcceleratedEffectProperty::OffsetAnchor: