Index database before getting Uri Descendants

onGetSliceDescendants would return empty results if
the call was made before the database was indexed.
This CL checks the index before building the list.

Change-Id: I2e0f88893138a048dbd529d465d68fa4b1a3dc12
Fixes: 78196823
Test: robotests

tests/robotests/src/com/android/settings/testutils/FakeIndexProvider.java

@@ -0,0 +1,54 @@
+/*
+ * 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.testutils;
+
+import android.content.Context;
+import android.provider.SearchIndexableResource;
+
+import com.android.settings.R;
+import com.android.settings.search.BaseSearchIndexProvider;
+import com.android.settings.search.Indexable;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FakeIndexProvider implements Indexable {
+
+    public static final String KEY = "TestKey";
+
+    public static final Indexable.SearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
+            new BaseSearchIndexProvider() {
+                @Override
+                public List<SearchIndexableResource> getXmlResourcesToIndex(Context context,
+                        boolean enabled) {
+                    List<SearchIndexableResource> resources = new ArrayList<>();
+                    SearchIndexableResource res = new SearchIndexableResource(context);
+                    res.xmlResId = R.xml.location_settings;
+                    resources.add(res);
+                    return resources;
+                }
+
+                @Override
+                public List<String> getNonIndexableKeys(Context context) {
+                    List<String> result = super.getNonIndexableKeys(context);
+                    result.add(KEY);
+                    return result;
+                }
+            };
+
+}