Restore the style of the screen saver widget from switch style to

button style.

The operation of the Switch is not suitable for previewing the
screen saver and will make the user confused. So we change the
style of the screen saver widget back to the button style.

Fix: 189505023
Test: manually test the screen saver
Change-Id: I4a97d91cc0b76111d4cb7b6aa202f2207ee0ca5d

res/layout/dream_start_button.xml

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2021 The Android Open Source Project
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+  -->
+
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:orientation="horizontal"
+    android:gravity="bottom"
+    android:paddingStart="72dp"
+    android:paddingEnd="72dp"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <Button
+        android:id="@+id/dream_start_now_button"
+        style="@style/ActionPrimaryButton"
+        android:layout_width="0dp"
+        android:layout_weight="1"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center"
+        android:text="@string/screensaver_settings_dream_start"/>
+
+</LinearLayout>