GPUExternalTextureDescriptor: fix compilation without video support

https://bugs.webkit.org/show_bug.cgi?id=262039

Reviewed by Mike Wyrzykowski.

Commit ac63088 accidentally readded
mediaIdentifier which was dropped in commit f9d7fea.

Signed-off-by: Thomas Devoogdt <thomas@devoogdt.com>
Canonical link: https://commits.webkit.org/268475@main

Source/WebCore/Modules/WebGPU/GPUExternalTextureDescriptor.h

@@ -63,14 +63,13 @@ struct GPUExternalTextureDescriptor : public GPUObjectDescriptorBase {
 
     WebGPU::ExternalTextureDescriptor convertToBacking() const
     {
-#if ENABLE(VIDEO)
-        auto mediaIdentifier = mediaIdentifierForSource(source);
-#else
-        auto mediaIdentifier = WebGPU::VideoSourceIdentifier { 0 };
-#endif
         return {
             { label },
+#if ENABLE(VIDEO)
             mediaIdentifierForSource(source),
+#else
+            { 0 },
+#endif
             WebCore::convertToBacking(colorSpace),
         };
     }