Fork Babel config and reduce supported browsers

Author: taneliang

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

@@ -0,0 +1,33 @@
+module.exports = api => {
+  const isTest = api.env('test');
+
+  const plugins = [
+    ['@babel/plugin-transform-flow-strip-types'],
+    ['@babel/plugin-proposal-class-properties', {loose: false}],
+
+    // The plugins below fix compilation errors on Webpack 4.
+    // See: https://github.com/webpack/webpack/issues/10227
+    // TODO: Remove once we're on Webpack 5.
+    ['@babel/plugin-proposal-optional-chaining'],
+    ['@babel/plugin-proposal-nullish-coalescing-operator'],
+  ];
+  if (process.env.NODE_ENV !== 'production') {
+    plugins.push(['@babel/plugin-transform-react-jsx-source']);
+  }
+
+  return {
+    plugins,
+    presets: [
+      [
+        '@babel/preset-env',
+        {
+          targets: isTest
+            ? {node: 'current'}
+            : 'last 2 Chrome versions, last 2 Firefox versions',
+        },
+      ],
+      '@babel/preset-react',
+      '@babel/preset-flow',
+    ],
+  };
+};

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

@@ -27,12 +27,7 @@ const DEVTOOLS_VERSION = getVersionString();
 const imageInlineSizeLimit = 10000;
 
 const babelOptions = {
-  configFile: resolve(
-    __dirname,
-    '..',
-    'react-devtools-shared',
-    'babel.config.js',
-  ),
+  configFile: resolve(__dirname, 'babel.config.js'),
   plugins: shouldUseDevServer
     ? [resolve(builtModulesDir, 'react-refresh/babel')]
     : [],