In apps with no channels, provide settings for misc channel in top level.

Test: robolectric tests pass, plus manual verification
Bug: 36561295

Change-Id: I58872a41fab562787d85bade0552c7735d716e5b

res/xml/legacy_channel_notification_settings.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2017 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.
+-->
+
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
+                  xmlns:settings="http://schemas.android.com/apk/res/com.android.settings" >
+
+
+    <!-- Importance toggle -->
+    <com.android.settingslib.RestrictedSwitchPreference
+        android:key="allow_sound"
+        android:title="@string/allow_sound" />
+
+    <!-- Visibility Override -->
+    <com.android.settings.notification.RestrictedDropDownPreference
+        android:key="visibility_override"
+        android:title="@string/app_notification_visibility_override_title" />
+
+    <!-- Bypass DND -->
+    <com.android.settingslib.RestrictedSwitchPreference
+        android:key="bypass_dnd"
+        android:title="@string/app_notification_override_dnd_title"
+        android:summary="@string/app_notification_override_dnd_summary"
+        settings:useAdditionalSummary="true" />
+
+</PreferenceScreen>