windows: fixes "class not registered" error

src/windows/BarcodeScannerProxy.js

@@ -116,7 +116,8 @@ module.exports = {
          */
         function startBarcodeSearch(width, height) {
 
-            reader = new WinRTBarcodeReader.Reader(capture, width, height);
+            reader = new WinRTBarcodeReader.Reader();
+            reader.init(capture, width, height);
             reader.readCode().done(function (result) {
                 destroyPreview();
                 success({ text: result && result.text, format: result && result.barcodeFormat, cancelled: !result });

src/windows/lib/WinRTBarcodeReader/WinRTBarcodeReader/Reader.cs

@@ -32,22 +32,22 @@ public sealed class Reader
         /// <summary>
         ///     Data reader, used to create bitmap array.
         /// </summary>
-        private readonly BarcodeReader barcodeReader;
+        private BarcodeReader barcodeReader;
 
         /// <summary>
         ///     The cancel search flag.
         /// </summary>
-        private readonly CancellationTokenSource cancelSearch;
+        private CancellationTokenSource cancelSearch;
 
         /// <summary>
         ///     MediaCapture instance, used for barcode search.
         /// </summary>
-        private readonly MediaCapture capture;
+        private MediaCapture capture;
 
         /// <summary>
         ///     Encoding properties for mediaCapture object.
         /// </summary>
-        private readonly ImageEncodingProperties encodingProps;
+        private ImageEncodingProperties encodingProps;
 
         /// <summary>
         ///     Flag that indicates successful barcode search.
@@ -69,7 +69,7 @@ public sealed class Reader
         /// <param name="capture">MediaCapture instance.</param>
         /// <param name="width">Capture frame width.</param>
         /// <param name="height">Capture frame height.</param>
-        public Reader(MediaCapture capture, uint width, uint height)
+        public void Init(MediaCapture capture, uint width, uint height)
         {
             this.capture = capture;
             encodingProps = ImageEncodingProperties.CreateJpeg();