Fix IE11 split (#5056)

src/SignalR/clients/ts/signalr/src/browser-index.ts

@@ -17,7 +17,8 @@ if (!Uint8Array.prototype.indexOf) {
 if (!Uint8Array.prototype.slice) {
     Object.defineProperty(Uint8Array.prototype, "slice", {
         // wrap the slice in Uint8Array so it looks like a Uint8Array.slice call
-        value: (start?: number, end?: number) => new Uint8Array(Array.prototype.slice(start, end)),
+        // tslint:disable-next-line:object-literal-shorthand
+        value: function(start?: number, end?: number) { return new Uint8Array(Array.prototype.slice.call(this, start, end)); },
         writable: true,
     });
 }