How to configure multiple java source directories using Android Studio Experimental Grade plugin?

Using Android Studio 2.1.1 with Experimental Grade plugin 0.7.2, I'm trying to add another Java source code directory to the module. Here's the relevant section from the module Gradle settings:

android.sources {
    main {
        java.source {
            //srcDir "src/java"
            //srcDir "../../JavaBindings/java"
            //srcDirs += "src"
            srcDirs += "../../JavaBindings/java"  <--- DOES NOT WORK
        }
        jni.source {
            srcDirs += "../../JavaBindings/jni"  <--- THIS WORKS
        }
    }
}

After looking around on Google and Stack Overflow, I tried a number of different syntaxes, but no luck. The app/java directory in the Android Studio project structure UI only shows what's in src/java and does not include what's in ../../JavaBindings/java.

However for the app/jni directory, it works: both what's in src/jni and ../../JavaBindings/jni shows up.

After looking at the source code for the Gradle Experimental plug-in, I eventually figured it out:

java.source.srcDirs and jni.source.srcDirs do not behave the same: for the JNI case, even if you define the jni.source.srcDirs setting, src/main/jni is always included by default, but that's not the case for the Java case.

So the correct syntax becomes:

android.sources {
    main {
        java.source {
            srcDirs += "src/main/java"
            srcDirs += "../../JavaBindings/java"
        }
        jni.source {
            srcDirs += "../../JavaBindings/jni"
        }
    }
}