[threaded-animation-resolution] avoid uploading a new effect stack to…

… the UIProcess if it remains empty

https://bugs.webkit.org/show_bug.cgi?id=269451

Reviewed by Dean Jackson.

Fix the `GraphicsLayerCA::setAcceleratedEffectsAndBaseValues()` method to return early if the effect stack
remains empty in order to avoid a layer property change and a subsequent upload to the UIProcess.

* Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp:
(WebCore::GraphicsLayerCA::setAcceleratedEffectsAndBaseValues):

Canonical link: https://commits.webkit.org/274754@main

Source/WebCore/platform/graphics/ca/GraphicsLayerCA.cpp

@@ -5041,8 +5041,14 @@ RefPtr<GraphicsLayerAsyncContentsDisplayDelegate> GraphicsLayerCA::createAsyncCo
 #if ENABLE(THREADED_ANIMATION_RESOLUTION)
 void GraphicsLayerCA::setAcceleratedEffectsAndBaseValues(AcceleratedEffects&& effects, AcceleratedEffectValues&& baseValues)
 {
+    auto hadEffectStack = !!acceleratedEffectStack();
+
     GraphicsLayer::setAcceleratedEffectsAndBaseValues(WTFMove(effects), WTFMove(baseValues));
 
+    // Nothing to do if we didn't have an accelerated stack and we still don't.
+    if (!hadEffectStack && !acceleratedEffectStack())
+        return;
+
     auto* layer = primaryLayer();
     ASSERT(layer);