GTTF: Add missing virtual destructors.

chrome/browser/ui/panels/display_settings_provider.h

Index: chrome/browser/ui/panels/display_settings_provider.h
diff --git a/chrome/browser/ui/panels/display_settings_provider.h b/chrome/browser/ui/panels/display_settings_provider.h
index 61a7a9970c595e1a98f38f5b061bb07133d056e5..461d9206f5e1bb5afcf59da751be229000651a3b 100644
--- a/chrome/browser/ui/panels/display_settings_provider.h
+++ b/chrome/browser/ui/panels/display_settings_provider.h
@@ -33,17 +33,26 @@ class DisplaySettingsProvider {
   class DisplayAreaObserver {
    public:
     virtual void OnDisplayAreaChanged(const gfx::Rect& display_area) = 0;
+
+   protected:
+    virtual ~DisplayAreaObserver() { }
   };
 
   class DesktopBarObserver {
    public:
     virtual void OnAutoHidingDesktopBarVisibilityChanged(
         DesktopBarAlignment alignment, DesktopBarVisibility visibility) = 0;
+
+   protected:
+    virtual ~DesktopBarObserver() { }
   };
 
   class FullScreenObserver {
    public:
     virtual void OnFullScreenModeChanged(bool is_full_screen) = 0;
+
+   protected:
+    virtual ~FullScreenObserver() { }
   };
 
   static DisplaySettingsProvider* Create();