Web Inspector: No reasons for compositing for an element with clip-pa…

…th and composited descendants

https://bugs.webkit.org/show_bug.cgi?id=242590

Reviewed by Simon Fraser.

If an element has clip-path and composited descendants, it has a
composited layer. However, Web Inspector didn't show no reason for
"Reasons for compositing" in the Layers tab.

* Source/WebCore/rendering/RenderLayerCompositor.cpp:
(WebCore::RenderLayerCompositor::reasonsForCompositing const):
Add CompositingReason::ClipsCompositingDescendants if hasClipPath.

Canonical link: https://commits.webkit.org/252354@main

Source/WebCore/rendering/RenderLayerCompositor.cpp

@@ -2796,6 +2796,8 @@ OptionSet<CompositingReason> RenderLayerCompositor::reasonsForCompositing(const
         if (layer.hasBlendMode())
             reasons.add(CompositingReason::BlendingWithCompositedDescendants);
 #endif
+        if (renderer.hasClipPath())
+            reasons.add(CompositingReason::ClipsCompositingDescendants);
         break;
     case IndirectCompositingReason::Perspective:
         reasons.add(CompositingReason::Perspective);