diff --git a/widget/src/gtk/nsNativeThemeGTK.cpp b/widget/src/gtk/nsNativeThemeGTK.cpp
index c7ccebe0beb4..fe055b57cab9 100644
--- a/widget/src/gtk/nsNativeThemeGTK.cpp
+++ b/widget/src/gtk/nsNativeThemeGTK.cpp
@@ -333,9 +333,10 @@ nsNativeThemeGTK::GetWidgetBorder(nsIDeviceContext* aContext,
 NS_IMETHODIMP
 nsNativeThemeGTK::GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                        PRUint8 aWidgetType,
-                                       nsSize* aResult)
+                                       nsSize* aResult, PRBool* aIsOverridable)
 {
   aResult->width = aResult->height = 0;
+  *aIsOverridable = PR_TRUE;
 
   switch (aWidgetType) {
     case NS_THEME_SCROLLBAR_BUTTON_UP:
diff --git a/widget/src/gtk/nsNativeThemeGTK.h b/widget/src/gtk/nsNativeThemeGTK.h
index 324313e4f83b..ece202714b28 100644
--- a/widget/src/gtk/nsNativeThemeGTK.h
+++ b/widget/src/gtk/nsNativeThemeGTK.h
@@ -62,7 +62,8 @@ public:
 
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
-                                  nsSize* aResult);
+                                  nsSize* aResult,
+                                  PRBool* aIsOverridable);
 
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint);
diff --git a/widget/src/gtk2/nsNativeThemeGTK.cpp b/widget/src/gtk2/nsNativeThemeGTK.cpp
index c7ccebe0beb4..fe055b57cab9 100644
--- a/widget/src/gtk2/nsNativeThemeGTK.cpp
+++ b/widget/src/gtk2/nsNativeThemeGTK.cpp
@@ -333,9 +333,10 @@ nsNativeThemeGTK::GetWidgetBorder(nsIDeviceContext* aContext,
 NS_IMETHODIMP
 nsNativeThemeGTK::GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                        PRUint8 aWidgetType,
-                                       nsSize* aResult)
+                                       nsSize* aResult, PRBool* aIsOverridable)
 {
   aResult->width = aResult->height = 0;
+  *aIsOverridable = PR_TRUE;
 
   switch (aWidgetType) {
     case NS_THEME_SCROLLBAR_BUTTON_UP:
diff --git a/widget/src/gtk2/nsNativeThemeGTK.h b/widget/src/gtk2/nsNativeThemeGTK.h
index 324313e4f83b..ece202714b28 100644
--- a/widget/src/gtk2/nsNativeThemeGTK.h
+++ b/widget/src/gtk2/nsNativeThemeGTK.h
@@ -62,7 +62,8 @@ public:
 
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
-                                  nsSize* aResult);
+                                  nsSize* aResult,
+                                  PRBool* aIsOverridable);
 
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint);
diff --git a/widget/src/windows/nsNativeThemeWin.cpp b/widget/src/windows/nsNativeThemeWin.cpp
index bd0574f3151d..93da4d49c85b 100644
--- a/widget/src/windows/nsNativeThemeWin.cpp
+++ b/widget/src/windows/nsNativeThemeWin.cpp
@@ -783,12 +783,13 @@ nsNativeThemeWin::GetWidgetBorder(nsIDeviceContext* aContext,
 NS_IMETHODIMP
 nsNativeThemeWin::GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                        PRUint8 aWidgetType,
-                                       nsSize* aResult)
+                                       nsSize* aResult, PRBool* aIsOverridable)
 {
   if (!getThemePartSize)
     return NS_ERROR_FAILURE;
 
   (*aResult).width = (*aResult).height = 0;
+  *aIsOverridable = PR_TRUE;
 
   if (aWidgetType == NS_THEME_TOOLBOX || aWidgetType == NS_THEME_TOOLBAR || 
       aWidgetType == NS_THEME_STATUSBAR || aWidgetType == NS_THEME_PROGRESSBAR_CHUNK ||
@@ -964,4 +965,4 @@ NS_METHOD NS_NewNativeTheme(nsISupports *aOuter, REFNSIID aIID, void **aResult)
   if (!theme)
     return NS_ERROR_OUT_OF_MEMORY;
   return theme->QueryInterface(aIID, aResult);
-}
\ No newline at end of file
+}
diff --git a/widget/src/windows/nsNativeThemeWin.h b/widget/src/windows/nsNativeThemeWin.h
index f1271d70e705..10c761733204 100644
--- a/widget/src/windows/nsNativeThemeWin.h
+++ b/widget/src/windows/nsNativeThemeWin.h
@@ -45,7 +45,8 @@ public:
 
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
-                                  nsSize* aResult);
+                                  nsSize* aResult,
+                                  PRBool* aIsOverridable);
 
   NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, PRUint8 aWidgetType, 
                                 nsIAtom* aAttribute, PRBool* aShouldRepaint);