[WPE] Build fix when WPE_PLATFORM disabled after 277537@main

https://bugs.webkit.org/show_bug.cgi?id=272676

Reviewed by Carlos Garcia Campos.

Function 'primaryScreenDisplayID' is only availble is WPE_PLATFORM is defined.

* Source/WebCore/platform/wpe/PlatformScreenWPE.cpp:
(WebCore::fontDPI):
* Source/WebKit/UIProcess/API/glib/WebKitProtocolHandler.cpp:
(WebKit::WebKitProtocolHandler::handleGPU):

Canonical link: https://commits.webkit.org/277609@main

Source/WebCore/platform/wpe/PlatformScreenWPE.cpp

@@ -107,8 +107,13 @@ double screenDPI(PlatformDisplayID screendisplayID)
 
 double fontDPI()
 {
+#if ENABLE(WPE_PLATFORM)
     // In WPE, there is no notion of font scaling separate from device DPI.
     return screenDPI(primaryScreenDisplayID());
+#else
+    notImplemented();
+    return 96.;
+#endif
 }
 
 FloatRect screenRect(Widget* widget)

Source/WebKit/UIProcess/API/glib/WebKitProtocolHandler.cpp

@@ -414,7 +414,9 @@ void WebKitProtocolHandler::handleGPU(WebKitURISchemeRequest* request)
     addTableRow(displayObject, "Depth"_s, String::number(screenDepth(nullptr)));
     addTableRow(displayObject, "Bits per color component"_s, String::number(screenDepthPerComponent(nullptr)));
     addTableRow(displayObject, "Font Scaling DPI"_s, String::number(fontDPI()));
+#if PLATFORM(GTK) || (PLATFORM(WPE) && ENABLE(WPE_PLATFORM))
     addTableRow(displayObject, "Screen DPI"_s, String::number(screenDPI(displayID.value_or(primaryScreenDisplayID()))));
+#endif
 
     if (displayID) {
         if (auto* displayLink = page.process().processPool().displayLinks().existingDisplayLinkForDisplay(*displayID)) {