Revert of Make createWindow (mostly) work with OOPIF

Source/platform/PlatformScreen.cpp

Index: Source/platform/PlatformScreen.cpp
diff --git a/Source/platform/PlatformScreen.cpp b/Source/platform/PlatformScreen.cpp
index dcfd0e4539e09afac93b1be341a2c19d5f6306f0..60b2ee3b8ba9518e73b1c6e9692fb4594a4b9940 100644
--- a/Source/platform/PlatformScreen.cpp
+++ b/Source/platform/PlatformScreen.cpp
@@ -80,9 +80,12 @@
     return IntRect(hostWindow->screenInfo().rect);
 }
 
-IntRect screenAvailableRect(const HostWindow& hostWindow)
+IntRect screenAvailableRect(Widget* widget)
 {
-    return IntRect(hostWindow.screenInfo().availableRect);
+    HostWindow* hostWindow = toHostWindow(widget);
+    if (!hostWindow)
+        return IntRect();
+    return IntRect(hostWindow->screenInfo().availableRect);
 }
 
 uint16_t screenOrientationAngle(Widget* widget)