Cannot lazily load firebase components

[jshcrowthe]

Describe your environment

• Operating System version: macOS Sierra
• Firebase SDK version: 4.0.0
• Firebase Product: app

Describe the problem

firebase.js is a really large file and while you can load the individual pieces of the SDK (firebase-app, firebase-database, firebase-auth, etc) you have to do so before calling firebase.initializeApp(). This, for most use cases, means that developers load the entire firebase SDK before their app code which results in a lot of time blocking the main thread.

Steps to reproduce:

1. Load firebase-app.js
2. Initialize an app with firebase.initializeApp()
3. Load firebase-database.js
4. Try and call firebase.database()
5. Observe error

Relevant Code:

http://jsbin.com/tovayaz/2/edit?js,console