Update

Updated cefsharp and removed flash.
But there is now a bug where the browser crashed when trying to download anything.

packages/CefSharp.Common.113.1.40/src/CefSharp.BrowserSubprocess.Core/JavascriptPromiseHandler.h

@@ -0,0 +1,89 @@
+// Copyright © 2020 The CefSharp Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+#pragma once
+
+#include "include/cef_v8.h"
+#include "..\CefSharp.Core.Runtime\Internals\Messaging\Messages.h"
+#include "..\CefSharp.Core.Runtime\Internals\Serialization\Primitives.h"
+#include "Serialization\V8Serialization.h"
+
+using namespace System;
+using namespace CefSharp::Internals::Messaging;
+using namespace CefSharp::BrowserSubprocess::Serialization;
+
+namespace CefSharp
+{
+    namespace BrowserSubprocess
+    {
+        const CefString kSendEvalScriptResponse = CefString("SendEvalScriptResponse");
+        const CefString kSendEvalScriptResponseCamelCase = CefString("sendEvalScriptResponse");
+
+        private class JavascriptPromiseHandler : public CefV8Handler
+        {
+        public:
+
+            virtual bool Execute(const CefString& name,
+                CefRefPtr<CefV8Value> object,
+                const CefV8ValueList& arguments,
+                CefRefPtr<CefV8Value>& retval,
+                CefString& exception)
+            {
+                if (arguments.size() < 2)
+                {
+                    //TODO: Improve error message
+                    exception = "Must specify a callback Id and then/catch.";
+
+                    return true;
+                }
+
+                auto callbackId = arguments[0]->GetIntValue();
+
+                if (callbackId == 0)
+                {
+                    exception = "Invalid callback Id";
+
+                    return true;
+                }
+
+                auto success = arguments[1]->GetBoolValue();
+                auto javascriptCallback = arguments.size() < 4 ? false : arguments[3]->GetBoolValue();
+
+                auto response = CefProcessMessage::Create(javascriptCallback ? kJavascriptCallbackResponse : kEvaluateJavascriptResponse);
+
+                auto responseArgList = response->GetArgumentList();
+                //Success
+                responseArgList->SetBool(0, success);
+                //Callback Id
+                SetInt64(responseArgList, 1, callbackId);
+                if (exception == "")
+                {
+                    if (success)
+                    {
+                        SerializeV8Object(arguments[2], responseArgList, 2, nullptr);
+                    }
+                    else
+                    {
+                        auto reason = arguments[2];
+                        responseArgList->SetString(2, reason->GetStringValue());
+                    }
+                }
+                else
+                {
+                    responseArgList->SetString(2, exception);
+                }
+
+                auto context = CefV8Context::GetCurrentContext();
+
+                auto frame = context->GetFrame();
+
+                frame->SendProcessMessage(CefProcessId::PID_BROWSER, response);
+
+                return false;
+            }
+
+            IMPLEMENT_REFCOUNTINGM(JavascriptPromiseHandler);
+        };
+    }
+}