Optimize http requests

MapboxSDKUnityCore.nuspec

@@ -41,6 +41,8 @@
 		<file src="bin\$configuration$\Mapbox.VectorTile.PbfReader.dll" target="content\sdkproject\Assets\Mapbox\Core\Plugins\MapboxVectorTile\"></file>
 		<file src="bin\$configuration$\Mapbox.VectorTile.VectorTileReader.dll" target="content\sdkproject\Assets\Mapbox\Core\Plugins\MapboxVectorTile\"></file>
 		<file src="bin\$configuration$\ICSharpCode.SharpZipLib.dll" target="content\sdkproject\Assets\Mapbox\Core\Plugins\ThirdParty\"></file>
+		<file src="bin\$configuration$\SmartThreadPool.dll" target="content\sdkproject\Assets\Mapbox\Core\Plugins\ThirdParty\"></file>
+		<file src="bin\$configuration$\System.Threading.dll" target="content\sdkproject\Assets\Mapbox\Core\Plugins\ThirdParty\"></file>
 <!--
 		<file src="bin\$configuration$\Triangulation.dll" target="content\sdkproject\Assets\Mapbox\Assets\Plugins\ThirdParty\"></file>
 -->

src/Map/IMemoryCache.cs

@@ -0,0 +1,11 @@
+//https://github.com/BruTile/BruTile
+// Copyright (c) BruTile developers team. All rights reserved. See License.txt in the project root for license information.
+
+namespace Mapbox.Map
+{
+    interface IMemoryCache<T> : ITileCache<T>
+    {
+        int MinTiles { get; set; }
+        int MaxTiles { get; set; }
+    }
+}

src/Map/ITileCache.cs

@@ -0,0 +1,16 @@
+//https://github.com/BruTile/BruTile
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Mapbox.Map
+{
+    public interface ITileCache<T>
+    {
+        void Add(CanonicalTileId tileId, T tile);
+        void Remove(CanonicalTileId tileId);
+        T Get(CanonicalTileId tileId);
+    }
+}