do not resize the canvas icon if a background image is not being used

Change-Id: If601bafd70beb7e0b5bf995727055f3685a8a03d

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

@@ -8,6 +8,7 @@ package com.google.appinventor.client.editor.simple.components;
 import com.google.appinventor.client.editor.simple.SimpleEditor;
 import com.google.appinventor.client.editor.simple.palette.SimplePaletteItem;
 import com.google.appinventor.client.widgets.dnd.DragSource;
+import com.google.gwt.user.client.DOM;
 import com.google.gwt.user.client.ui.AbsolutePanel;
 
 import java.util.Comparator;
@@ -83,12 +84,15 @@ public final class MockCanvas extends MockContainer {
       // text was not recognized as an asset.
       ((MockCanvasLayout) layout).setBackgroundImageUrl("");
       url = "images/canvas.png";
+      // We set the background image of the canvasWidget so it displays the image. We do it inside
+      // the if because we need to override the background-size property only for this case
+      MockComponentsUtil.setWidgetBackgroundImage(canvasWidget, url);
+      DOM.setStyleAttribute(canvasWidget.getElement(), "backgroundSize", "");
     } else {
       ((MockCanvasLayout) layout).setBackgroundImageUrl(url);
+      // We set the background image of the canvasWidget so it displays the image.
+      MockComponentsUtil.setWidgetBackgroundImage(canvasWidget, url);
     }
-
-    // We set the background image of the canvasWidget so it displays the image.
-    MockComponentsUtil.setWidgetBackgroundImage(canvasWidget, url);
   }
 
   private static class MockSpriteWithCoordinates {