Test - Use SwANGLE

  - Use --use-gl=angle --use-angle=swiftshader command line arg

Tests are still failing sometimes due to GPU crash. We cannot add an app.manifest to the test runner, so hopefully this helps.

https://ci.appveyor.com/project/cefsharp/cefsharp/builds/52468153#L1912

Author: amaitland

CefSharp.Test/CefSharpFixture.cs

@@ -66,6 +66,8 @@ private void CefInitialize()
                 //settings.CefCommandLineArgs.Add("renderer-startup-dialog");
                 //settings.CefCommandLineArgs.Add("disable-site-isolation-trials");
                 settings.SetOffScreenRenderingBestPerformanceArgs();
+                settings.CefCommandLineArgs.Add("use-gl", "angle");
+                settings.CefCommandLineArgs.Add("use-angle", "swiftshader");
 
                 var success = Cef.Initialize(settings, performDependencyCheck: false, browserProcessHandler: null);