Preparation for syncing sources with internal repo (dotnet#275)

* make class partial so I can add constuctor in separate file. add constructros for testing

* formatting

src/Microsoft.ML.Sweeper/AsyncSweeper.cs

@@ -63,7 +63,7 @@ public interface IAsyncSweeper
     /// Expose existing <see cref="ISweeper"/>s as <see cref="IAsyncSweeper"/> with no synchronization over the past runs.
     /// Nelder-Mead requires synchronization so is not compatible with SimpleAsyncSweeperBase.
     /// </summary>
-    public class SimpleAsyncSweeper : IAsyncSweeper, IDisposable
+    public partial class SimpleAsyncSweeper : IAsyncSweeper, IDisposable
     {
         private readonly List<IRunResult> _results;
         private readonly object _lock;
@@ -85,6 +85,16 @@ private SimpleAsyncSweeper(ISweeper baseSweeper)
             _results = new List<IRunResult>();
         }
 
+        public SimpleAsyncSweeper(IHostEnvironment env, UniformRandomSweeper.ArgumentsBase args)
+            : this(new UniformRandomSweeper(env, args))
+        {
+        }
+
+        public SimpleAsyncSweeper(IHostEnvironment env, RandomGridSweeper.Arguments args)
+            : this(new UniformRandomSweeper(env, args))
+        {
+        }
+
         public void Update(int id, IRunResult result)
         {
             Contracts.CheckParam(0 <= id && id < _numGenerated, nameof(id), "Invalid run id");