Add support for Auto Backup for Apps

mobile/src/main/AndroidManifest.xml

@@ -20,6 +20,8 @@
         android:name=".App"
         android:icon="@mipmap/ic_launcher"
         android:backupAgent=".ConfigBackupHelper"
+        android:fullBackupContent="@xml/backup_descriptor"
+        android:fullBackupOnly="true"
         android:label="@string/app_name"
         android:supportsRtl="true"
         android:networkSecurityConfig="@xml/network_security_config"

mobile/src/main/java/com/github/shadowsocks/ConfigBackupHelper.kt

@@ -25,6 +25,7 @@ import android.app.backup.FileBackupHelper
 import com.github.shadowsocks.acl.Acl
 import com.github.shadowsocks.utils.Key
 
+@Deprecated("Only used in API level < 23. For 6.0+, Auto Backup for Apps is used.")
 class ConfigBackupHelper : BackupAgentHelper() {
     override fun onCreate() = addHelper("com.github.shadowsocks.database.profile",
             FileBackupHelper(this, "../databases/" + Key.PROFILE, Acl.CUSTOM_RULES + ".acl"))

mobile/src/main/res/xml/backup_descriptor.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<full-backup-content>
+    <include domain="database" path="profile.db"/>
+    <include domain="file" path="custom-rules.acl"/>
+</full-backup-content>