Core - EvaluateScriptAsync no longer returns meaningful error messages

Resolves #4629

Author: amaitland

CefSharp.Core.Runtime/Internals/StringUtils.h

@@ -133,10 +133,10 @@ namespace CefSharp
                 if (exception.get())
                 {
                     std::wstringstream logMessageBuilder;
-                    logMessageBuilder << exception->GetMessage().c_str() << L"\n@ ";
+                    logMessageBuilder << exception->GetMessage().ToWString() << L"\n@ ";
                     if (!exception->GetScriptResourceName().empty())
                     {
-                        logMessageBuilder << exception->GetScriptResourceName().c_str();
+                        logMessageBuilder << exception->GetScriptResourceName().ToWString();
                     }
                     logMessageBuilder << L":" << exception->GetLineNumber() << L":" << exception->GetStartColumn();
                     return CefString(logMessageBuilder.str());

CefSharp.Test/Javascript/EvaluateScriptAsyncTests.cs

@@ -216,6 +216,18 @@ public async Task CanEvaluateScriptAsyncReturnPartiallyEmptyArrays(string javasc
             Assert.Equal(expected, result.Result);
         }
 
+        [Theory]
+        [InlineData("return", "Uncaught SyntaxError: Illegal return statement\n@ about:blank:1:0")]
+        public async Task CanEvaluateScriptAsyncReturnError(string javascript, string expected)
+        {
+            AssertInitialLoadComplete();
+
+            var result = await Browser.EvaluateScriptAsync(javascript);
+
+            Assert.False(result.Success);
+            Assert.Equal(expected, result.Message);
+        }
+
         /// <summary>
         /// Use the EvaluateScriptAsync (IWebBrowser, String,Object[]) overload and pass in string params
         /// that require encoding. Test case for https://github.com/cefsharp/CefSharp/issues/2339