Ownership of Platform in part of the code.

dw/layout.hh

@@ -157,7 +157,7 @@ private:
       ~Anchor ();
    };
 
-   Platform *platform;
+   std::unique_ptr< Platform > platform;
    View *view;
    std::unique_ptr< Widget > topLevel;
    Widget *widgetAtPoint;
@@ -349,7 +349,7 @@ public:
 
    inline Platform *getPlatform ()
    {
-      return platform;
+      return platform.get();
    }
 
    /* delegated */