Updated scheduling profiler Webpack config

1. Don't conflict with DevTools test shell port.
2. Add __VARIANT__ global since this is referenced in code now.

Author: Brian Vaughn

packages/react-devtools-scheduling-profiler/webpack.config.js

@@ -56,6 +56,7 @@ const config = {
       __DEV__,
       __PROFILE__: false,
       __EXPERIMENTAL__: true,
+      __VARIANT__: false,
       'process.env.DEVTOOLS_VERSION': `"${DEVTOOLS_VERSION}"`,
     }),
     new HtmlWebpackPlugin({
@@ -112,7 +113,7 @@ const config = {
 if (shouldUseDevServer) {
   config.devServer = {
     hot: true,
-    port: 8080,
+    port: 8081,
     clientLogLevel: 'warning',
     stats: 'errors-only',
   };