REGRESSION(266149@main): RemoteRenderingBackendProxy.h(126): error C3…

…646: 'displayRequirement': unknown override specifier

https://bugs.webkit.org/show_bug.cgi?id=259330

Unreviewed build fix for Windows port.
It was broken by 266149@main (bug#259316).

> WebProcess\GPU\graphics\RemoteRenderingBackendProxy.h(126): error C3646: 'displayRequirement': unknown override specifier
> WebProcess\GPU\graphics\RemoteRenderingBackendProxy.h(126): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

* Source/WebKit/WebProcess/GPU/graphics/RemoteRenderingBackendProxy.h:
Guard SwapBuffersResult by PLATFORM(COCOA).

Canonical link: https://commits.webkit.org/266152@main

Source/WebKit/WebProcess/GPU/graphics/RemoteRenderingBackendProxy.h

@@ -121,12 +121,12 @@ class RemoteRenderingBackendProxy
         bool hasEmptyDirtyRegion { false };
     };
 
+#if PLATFORM(COCOA)
     struct SwapBuffersResult {
         BufferSet buffers;
         SwapBuffersDisplayRequirement displayRequirement;
     };
 
-#if PLATFORM(COCOA)
     Vector<SwapBuffersResult> prepareBuffersForDisplay(const Vector<LayerPrepareBuffersData>&);
 #endif