Use ViewStub for setEmptyView (bug 1803058)

and use <merge> instead of FrameLayout
diff --git a/res/layout/browser_downloads_page.xml b/res/layout/browser_downloads_page.xml
index c83a727..1d4d4e6 100644
--- a/res/layout/browser_downloads_page.xml
+++ b/res/layout/browser_downloads_page.xml
@@ -18,8 +18,14 @@
 ** limitations under the License.
 */
 -->
-
-<ListView xmlns:android="http://schemas.android.com/apk/res/android"
-    android:id="@+id/list"
-    android:layout_width="fill_parent"
-    android:layout_height="fill_parent"/>
+<merge xmlns:android="http://schemas.android.com/apk/res/android">
+    <ListView 
+        android:id="@+id/list"
+        android:layout_width="fill_parent"
+        android:layout_height="fill_parent"/>
+    <ViewStub 
+        android:id="@+id/empty"
+        android:layout="@layout/no_downloads"
+        android:layout_width="fill_parent"
+        android:layout_height="fill_parent"/>
+</merge>