Support v2 playgrounds in visual tests (#1560)

All new playgrounds are serialized in the v2 format, so this is bare
minimum to support that.

Author: alexchuber

Apps/Playground/Scripts/validation_native.js

@@ -179,7 +179,22 @@
                         try {
                             xmlHttp.onreadystatechange = null;
                             const snippet = JSON.parse(xmlHttp.responseText);
-                            let code = JSON.parse(snippet.jsonPayload).code.toString()
+                            let code = JSON.parse(snippet.jsonPayload).code.toString();
+
+                            // Check if this is a v2 manifest and extract the entry file's code
+                            // TODO: Handle multi-file playgrounds
+                            try {
+                                const manifestPayload = JSON.parse(code);
+                                if (manifestPayload.v === 2) {
+                                    code = manifestPayload.files[manifestPayload.entry]
+                                        .replace(/export +default +/g, "")
+                                        .replace(/export +/g, "");
+                                }
+                            } catch (e) {
+                                // Not a manifest, proceed as usual
+                            }
+
+                            code = code
                                 .replace(/"\/textures\//g, '"' + pgRoot + "/textures/")
                                 .replace(/"textures\//g, '"' + pgRoot + "/textures/")
                                 .replace(/\/scenes\//g, pgRoot + "/scenes/")