Fixes a problem resizing Images inside other containers such as Buttons, Canvas, and Screen

background. They used to get clipped instead of resizing correctly, only in the
Designer.

Change-Id: I445c542b5fcc158b28b3306bf97e3a53a4f125a0

appinventor/appengine/src/com/google/appinventor/client/editor/simple/components/MockComponentsUtil.java

@@ -45,6 +45,7 @@ public final class MockComponentsUtil {
     DOM.setStyleAttribute(widget.getElement(), "backgroundImage", "url(" + image + ')');
     DOM.setStyleAttribute(widget.getElement(), "backgroundRepeat", "no-repeat");
     DOM.setStyleAttribute(widget.getElement(), "backgroundPosition", "center");
+    DOM.setStyleAttribute(widget.getElement(), "backgroundSize", "100% 100%");
   }
 
   /**