[WebGPU] Device::createRenderPipeline will crash (MTLReportFailure) i…

…f fragmentDescriptor.targetCount > 8

https://bugs.webkit.org/show_bug.cgi?id=265851
<radar://119169360>

Reviewed by Dan Glastonbury.

Further validation will be added but this prevents a crash
while running the CTS when more than 8 color targets are used.

* Source/WebGPU/WebGPU/RenderPipeline.mm:
(WebGPU::Device::validateRenderPipeline):

Canonical link: https://commits.webkit.org/271540@main

Source/WebGPU/WebGPU/RenderPipeline.mm

@@ -193,7 +193,12 @@ static MTLPrimitiveTopologyClass topologyType(WGPUPrimitiveTopology topology)
     // FIXME: Implement this according to the description in
     // https://gpuweb.github.io/gpuweb/#abstract-opdef-validating-gpurenderpipelinedescriptor
 
-    UNUSED_PARAM(descriptor);
+    if (descriptor.fragment) {
+        const auto& fragmentDescriptor = *descriptor.fragment;
+
+        if (fragmentDescriptor.targetCount > limits().maxColorAttachments)
+            return false;
+    }
 
     return true;
 }