Restoring pinned shortcuts to original state after restore

Creating an no-op backup agent in settings. This ensures that
we get onRestoreFinished callback after restore is finished where we
can update all pinned shortcuts.

Bug: 110016648
Test: Verified backup->clear-data->restore path on device
Change-Id: Id14d0792d60ba08d97078a31a81d2b63ab8ce109

src/com/android/settings/backup/SettingsBackupHelper.java

@@ -0,0 +1,89 @@
+/**
+ * Copyright (C) 2019 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.backup;
+
+import android.app.backup.BackupAgentHelper;
+import android.app.backup.BackupDataInputStream;
+import android.app.backup.BackupDataOutput;
+import android.app.backup.BackupHelper;
+import android.os.ParcelFileDescriptor;
+
+import com.android.settings.shortcut.CreateShortcutPreferenceController;
+
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+/**
+ * Backup agent for Settings APK
+ */
+public class SettingsBackupHelper extends BackupAgentHelper {
+
+    @Override
+    public void onCreate() {
+        super.onCreate();
+        addHelper("no-op", new NoOpHelper());
+    }
+
+    @Override
+    public void onRestoreFinished() {
+        super.onRestoreFinished();
+        CreateShortcutPreferenceController.updateRestoredShortcuts(this);
+    }
+
+    /**
+     * Backup helper which does not do anything. Having at least one helper ensures that the
+     * transport is not empty and onRestoreFinished is called eventually.
+     */
+    private static class NoOpHelper implements BackupHelper {
+
+        private final int VERSION_CODE = 1;
+
+        @Override
+        public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
+                ParcelFileDescriptor newState) {
+
+            try (FileOutputStream out = new FileOutputStream(newState.getFileDescriptor())) {
+                if (getVersionCode(oldState) != VERSION_CODE) {
+                    data.writeEntityHeader("dummy", 1);
+                    data.writeEntityData(new byte[1], 1);
+                }
+
+                // Write new version code
+                out.write(VERSION_CODE);
+                out.flush();
+            } catch (IOException e) { }
+        }
+
+        @Override
+        public void restoreEntity(BackupDataInputStream data) { }
+
+        @Override
+        public void writeNewStateDescription(ParcelFileDescriptor newState) { }
+
+        private int getVersionCode(ParcelFileDescriptor state) {
+            if (state == null) {
+                return 0;
+            }
+            try (FileInputStream in = new FileInputStream(state.getFileDescriptor())) {
+                return in.read();
+            } catch (IOException e) {
+                return 0;
+            }
+        }
+    }
+}