How to make Android Studio download dependencies sources and javadoc?

For Maven sources and docs the only thing I have found is to change the default settings.

File -> Other Settings -> Default Settings... -> Maven -> Importing

Checking the boxes to download Sources and Documentation

As we can see the answer from Xavier Ducrohet (Android SDK Tech Lead Google Inc.), as of July 26, 2013:

I don't think Gradle handles this at this point. I've talked to the devs and they are aware of it. We're looking at adding a hook in Gradle so that we can do it when the tooling API queries the model.