Add shadow and wrapper classes

These classes are used for accessibility service. Also
add a new Availablity type.

Bug: 62022517
Test: Build
Change-Id: Ia2ff72dd04fd99b17809822907746c2411cecb62

src/com/android/settings/applications/AccessibilityServiceInfoWrapper.java

@@ -0,0 +1,37 @@
+/*
+ * 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.
+ */
+
+package com.android.settings.applications;
+
+import android.accessibilityservice.AccessibilityServiceInfo;
+import android.content.ComponentName;
+
+/**
+ * This interface replicates a subset of the
+ * {@link android.accessibilityservice.AccessibilityServiceInfo}. The interface
+ * exists so that we can use a thin wrapper around it in production code and a mock in tests.
+ * We cannot directly mock or shadow it, because some of the methods we rely on are newer than
+ * the API version supported by Robolectric.
+ */
+public interface AccessibilityServiceInfoWrapper {
+
+    /**
+     * Returns the real {@code AccessibilityServiceInfo} object.
+     */
+    AccessibilityServiceInfo getAccessibilityServiceInfo();
+
+    ComponentName getComponentName();
+}