Tidy up context creation

osu.Game/Database/OsuDbContext.cs

@@ -22,14 +22,29 @@ namespace osu.Game.Database
         public DbSet<RulesetInfo> RulesetInfo { get; set; }
         private readonly string connectionString;
 
-        public OsuDbContext()
+        static OsuDbContext()
         {
-            connectionString = "DataSource=:memory:";
+            // required to initialise native SQLite libraries on some platforms.
+            SQLitePCL.Batteries_V2.Init();
         }
 
-        public OsuDbContext(string connectionString)
+        /// <summary>
+        /// Create a new OsuDbContext instance.
+        /// </summary>
+        /// <param name="connectionString">A valid SQLite connection string. If not provided, an in-memory instance will be created.</param>
+        public OsuDbContext(string connectionString = "DataSource=:memory:")
         {
             this.connectionString = connectionString;
+
+            Database.SetCommandTimeout(new TimeSpan(TimeSpan.TicksPerSecond * 10));
+
+            var connection = Database.GetDbConnection();
+            connection.Open();
+            using (var cmd = connection.CreateCommand())
+            {
+                cmd.CommandText = "PRAGMA journal_mode=WAL;";
+                cmd.ExecuteNonQuery();
+            }
         }
 
         protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)

osu.Game/OsuGameBase.cs

@@ -81,21 +81,7 @@ namespace osu.Game
         protected override IReadOnlyDependencyContainer CreateLocalDependencies(IReadOnlyDependencyContainer parent) =>
             dependencies = new DependencyContainer(base.CreateLocalDependencies(parent));
 
-        private OsuDbContext createDbContext()
+        private OsuDbContext createDbContext() => new OsuDbContext(Host.Storage.GetDatabaseConnectionString(@"client"));
-        {
-            SQLitePCL.Batteries.Init();
-            var connectionString = Host.Storage.GetDatabaseConnectionString(@"client");
-            var context = new OsuDbContext(connectionString);
-            var connection = context.Database.GetDbConnection();
-            connection.Open();
-            using (var command = connection.CreateCommand())
-            {
-                command.CommandText = "PRAGMA journal_mode=WAL;";
-                command.ExecuteNonQuery();
-            }
-            context.Database.SetCommandTimeout(new TimeSpan(TimeSpan.TicksPerSecond * 10));
-            return context;
-        }
 
         [BackgroundDependencyLoader]
         private void load()