Add missing virtual destructors

src/app/ui/skin/skin_slider_property.h

@@ -34,6 +34,7 @@ namespace app {
 
     class ISliderBgPainter {
     public:
+      virtual ~ISliderBgPainter() { }
       virtual void paint(ui::Slider* slider, ui::Graphics* graphics, const gfx::Rect& rc) = 0;
     };
 

src/base/thread.h

@@ -53,6 +53,7 @@ namespace base {                // Based on C++0x threads lib
 
     class func_wrapper {
     public:
+      virtual ~func_wrapper() { }
       virtual void operator()() = 0;
     };