b=350763, add IsFirstTab/IsLastTab predicates to native theme xpwidget code, r=stuart

widget/src/xpwidgets/nsNativeTheme.cpp

@@ -329,6 +329,24 @@ nsNativeTheme::IsBottomTab(nsIFrame* aFrame)
   return !classStr.IsEmpty() && classStr.Find("tab-bottom") != kNotFound;
 }
 
+PRBool
+nsNativeTheme::IsFirstTab(nsIFrame* aFrame)
+{
+  if (!aFrame)
+    return PR_FALSE;
+
+  return aFrame->GetContent()->HasAttr(kNameSpaceID_None, nsWidgetAtoms::firsttab);
+}
+
+PRBool
+nsNativeTheme::IsLastTab(nsIFrame* aFrame)
+{
+  if (!aFrame)
+    return PR_FALSE;
+
+  return aFrame->GetContent()->HasAttr(kNameSpaceID_None, nsWidgetAtoms::lasttab);
+}
+
 // progressbar:
 PRBool
 nsNativeTheme::IsIndeterminateProgress(nsIFrame* aFrame)

widget/src/xpwidgets/nsNativeTheme.h

@@ -113,6 +113,8 @@ class nsNativeTheme
 
   // tab:
   PRBool IsBottomTab(nsIFrame* aFrame);
+  PRBool IsFirstTab(nsIFrame* aFrame);
+  PRBool IsLastTab(nsIFrame* aFrame);
 
   // progressbar:
   PRBool IsIndeterminateProgress(nsIFrame* aFrame);

widget/src/xpwidgets/nsWidgetAtomList.h

@@ -77,6 +77,7 @@ WIDGET_ATOM(image, "image")
 WIDGET_ATOM(input, "input")
 WIDGET_ATOM(key, "key") // The key element / attribute
 WIDGET_ATOM(label, "label")
+WIDGET_ATOM(lasttab, "last-tab")
 WIDGET_ATOM(maxpos, "maxpos")
 WIDGET_ATOM(menu, "menu") // Represents an XP menu
 WIDGET_ATOM(menuitem, "menuitem") // Represents an XP menu item