diff --git a/mozilla/dom/src/base/nsGlobalWindow.cpp b/mozilla/dom/src/base/nsGlobalWindow.cpp
index 1ddeb57aa1e..e7ffd8dce5d 100644
--- a/mozilla/dom/src/base/nsGlobalWindow.cpp
+++ b/mozilla/dom/src/base/nsGlobalWindow.cpp
@@ -2628,6 +2628,8 @@ PRUint32 GlobalWindowImpl::CalculateChromeFlags(char* aFeatures, PRBool aDialog)
 
    chromeFlags |= WinHasOption(aFeatures, "chrome", nsnull) ? 
       nsIWebBrowserChrome::openAsChrome : 0;
+   chromeFlags |= WinHasOption(aFeatures, "centerscreen", nsnull) ? 
+      nsIWebBrowserChrome::centerScreen : 0;
    chromeFlags |= WinHasOption(aFeatures, "dependent", nsnull) ? 
       nsIWebBrowserChrome::dependent : 0;
    chromeFlags |= WinHasOption(aFeatures, "modal", nsnull) ? 
diff --git a/mozilla/xpfe/appshell/src/nsAppShellService.cpp b/mozilla/xpfe/appshell/src/nsAppShellService.cpp
index f1d1968cd4b..5cb290320d0 100644
--- a/mozilla/xpfe/appshell/src/nsAppShellService.cpp
+++ b/mozilla/xpfe/appshell/src/nsAppShellService.cpp
@@ -589,6 +589,9 @@ nsAppShellService::JustCreateTopWindow(nsIXULWindow *aParent,
 #endif
 
     }
+
+    if (aChromeMask & nsIWebBrowserChrome::centerScreen)
+      window->Center(nsnull, PR_TRUE, PR_FALSE);
   }
 
   return rv;