Bug 801301 - Fix popup submenus opening behind their parent on Windows XP. r=roc

--HG--
extra : rebase_source : 25c1b7bf5db71b40130816d629c4d54707290a49

widget/windows/nsWindow.cpp

@@ -488,7 +488,8 @@ nsWindow::Create(nsIWidget *aParent,
       parent = NULL;
     }
 
-    if (mPopupType == ePopupTypeMenu && aInitData->mDropShadow) {
+    if (WinUtils::GetWindowsVersion() >= WinUtils::VISTA_VERSION &&
+        mPopupType == ePopupTypeMenu && aInitData->mDropShadow) {
       extendedStyle |= WS_EX_COMPOSITED;
     }