Fix minor bug in bg.js

A break statement was missing in a switch. This commit also fixes some
minor cosmetic issues reported by eslint in bg.js.

Change-Id: I01adfe262a315fb993c894c7f116b797ca4352e7
diff --git a/.eslintrc.json b/.eslintrc.json
index b110eaa..185c15a 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -15,5 +15,8 @@
     },
     "ignorePatterns": [
       "webpack.config.js"
-    ]
+    ],
+    "globals": {
+      "PRODUCTION": "readonly"
+    }
 }