e2e test for transformer (webdriver + pub serve)

package.json

Index: package.json
diff --git a/package.json b/package.json
index 207b823c8f1f46fd788dad3ca63cab4dddd2437b..8fc26a99c04eb7473c92a3bc55a4908ef00c1910 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "url": "https://github.com/dart-lang/dev_compiler.git"
   },
   "scripts": {
+    "postinstall": "./node_modules/.bin/webdriver-manager update",
     "test": "./node_modules/.bin/karma start --single-run"
   },
   "devDependencies": {
@@ -24,6 +25,7 @@
     "karma-mocha": "^0.1.10",
     "karma-requirejs": "^0.2.2",
     "mocha": "^2.2.4",
-    "requirejs": "^2.1.17"
+    "requirejs": "^2.1.17",
+    "webdriver-manager": "8.0.0"
   }
 }