fix clang error on cros

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148459 0039d316-1c4b-4281-b951-d872f2087c98

ash/wm/cursor_manager.h

@@ -20,7 +20,7 @@ class CursorDelegate;
 class CursorManager : public aura::client::CursorClient {
  public:
   CursorManager();
-  ~CursorManager();
+  virtual ~CursorManager();
 
   void set_delegate(CursorDelegate* delegate) { delegate_ = delegate; }