android: Don't show canvas elements by default

Change-Id: I32372660c78a0fa253fdfaf94b15ae823c4eb5ac

android/experimental/LOAndroid3/src/java/org/libreoffice/canvas/CommonCanvasElement.java

@@ -7,7 +7,7 @@ import android.graphics.Canvas;
  */
 public abstract class CommonCanvasElement implements CanvasElement {
 
-    private boolean mVisible = true;
+    private boolean mVisible = false;
 
     @Override
     public boolean isVisible() {