[release/6.0] [wasm][debugger] Fix (chrome|edge)://inspect for the de…

…bug proxy (#65219)

* Inspector wants the content-length set

* Use utf8 length

Co-authored-by: Larry Ewing <lewing@microsoft.com>

src/mono/wasm/debugger/BrowserDebugHost/Startup.cs

@@ -7,6 +7,7 @@
 using System.Linq;
 using System.Net.Http;
 using System.Text.Json;
+using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
@@ -139,7 +140,9 @@ async Task RewriteArray(HttpContext context)
                     Dictionary<string, string>[] tabs = await ProxyGetJsonAsync<Dictionary<string, string>[]>(GetEndpoint(context));
                     Dictionary<string, string>[] alteredTabs = tabs.Select(t => mapFunc(t, context, devToolsHost)).ToArray();
                     context.Response.ContentType = "application/json";
-                    await context.Response.WriteAsync(JsonSerializer.Serialize(alteredTabs));
+                    byte[] bytes = Encoding.UTF8.GetBytes(JsonSerializer.Serialize(alteredTabs));
+                    context.Response.ContentLength = bytes.Length;
+                    await context.Response.Body.WriteAsync(bytes);
                 }
 
                 async Task ConnectProxy(HttpContext context)