Use Babel for react-dev-utils

.eslintignore

@@ -3,3 +3,4 @@ build
 my-app*
 packages/react-scripts/template
 packages/react-scripts/fixtures
+packages/react-dev-utils/*.js

package.json

@@ -6,7 +6,7 @@
     "create-react-app": "node tasks/cra.js",
     "e2e": "tasks/e2e-simple.sh",
     "e2e:docker": "tasks/local-test.sh",
-    "postinstall": "node bootstrap.js && cd packages/react-error-overlay/ && npm run build:prod",
+    "postinstall": "node bootstrap.js && cd packages/react-dev-utils/ && npm run build:prod && cd ../react-error-overlay/ && npm run build:prod",
     "publish": "tasks/release.sh",
     "start": "node packages/react-scripts/scripts/start.js",
     "screencast": "svg-term --cast hItN7sl5yfCPTHxvFg5glhhfp --out screencast.svg --window",

packages/react-dev-utils/.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": ["react-app"]
+}

packages/react-dev-utils/.gitignore

@@ -0,0 +1 @@
+/*.js

packages/react-dev-utils/package.json

@@ -4,6 +4,14 @@
   "description": "Webpack utilities used by Create React App",
   "repository": "facebookincubator/create-react-app",
   "license": "MIT",
+  "scripts": {
+    "test": "jest",
+    "prepublish": "npm run build:prod",
+    "babel": "rimraf *.js && babel src/ -d ./",
+    "build": "cross-env NODE_ENV=development npm run babel",
+    "watch": "cross-env NODE_ENV=development npm run babel -- -w",
+    "build:prod": "cross-env NODE_ENV=production npm run babel"
+  },
   "bugs": {
     "url": "https://github.com/facebookincubator/create-react-app/issues"
   },
@@ -56,9 +64,10 @@
     "text-table": "0.2.0"
   },
   "devDependencies": {
+    "babel-cli": "6.24.1",
+    "babel-preset-react-app": "3.0.2",
+    "cross-env": "5.0.5",
+    "rimraf": "^2.6.1",
     "jest": "20.0.4"
-  },
-  "scripts": {
-    "test": "jest"
   }
 }