Fix icon padding in app notification settings.

Change-Id: I93da362f0bd6b3f388864a961c2365163c44e474
diff --git a/res/layout/notification_app_dialog.xml b/res/layout/notification_app_dialog.xml
index 5b2fd1a..bbd4846 100644
--- a/res/layout/notification_app_dialog.xml
+++ b/res/layout/notification_app_dialog.xml
@@ -19,10 +19,10 @@
 
     <ImageView
         android:id="@android:id/icon"
+        android:padding="8dp"
         android:layout_width="@dimen/notification_app_icon_size"
         android:layout_height="@dimen/notification_app_icon_size"
-        android:contentDescription="@null"
-        android:scaleType="center" />
+        android:contentDescription="@null" />
 
     <TextView
         android:id="@android:id/title"