Building Native Extension for Android - createExtensionContext returns null

Question

I've been trying to build a Native Extension in Adobe AIR for Android and stumbled across some issues. Looks like something is wrong with the configuration or the steps I take to build it.

I've created an ANEBoilerplate project so I can get down to the very basis of the problem. Here is the test code I use for it:

package
{
    import com.tomasz.boilerplate.BoilerplateAS;
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;

    public class BoilerplateTest extends Sprite
    {
        public function BoilerplateTest()
        {
            super();

            // support autoOrients
            stage.align = StageAlign.TOP_LEFT;
            stage.scaleMode = StageScaleMode.NO_SCALE;

            var ane:BoilerplateAS = new BoilerplateAS();
        }
    }

And here is the source of my AS3 side of the ANE [BoilerplateAS.as]:

package com.tomasz.boilerplate
{
    import flash.events.EventDispatcher;
    import flash.external.ExtensionContext;

    public class BoilerplateAS extends EventDispatcher
    {
        private var _extContext:ExtensionContext;

        public function BoilerplateAS()
        {
            super();
            _extContext = ExtensionContext.createExtensionContext("com.tomasz.boilerplate", "");
            if(!_extContext) {
                throw new Error("Boilerplate native extension is not supported on this platform.");
            }
        }
    }
}

The problem is I get _extContext equal null.

Here is my extension.xml:

<extension xmlns="http://ns.adobe.com/air/extension/19.0">
    <id>com.tomasz.boilerplate</id>
    <versionNumber>1</versionNumber>
    <platforms>
        <platform name="Android-ARM">
            <applicationDeployment>
                <nativeLibrary>classes.jar</nativeLibrary>
                                <initializer>com.tomasz.boilerplate.MainActivity</initializer>
                                <finalizer>com.tomasz.boilerplate.MainActivity</finalizer>
            </applicationDeployment>
        </platform>
    </platforms>
</extension>

And here is the structure of my extension directory:

And this is how I compile the ANE:

adt -package -target ane Boilerplate.ane extension.xml -swc BoilerplateAS.swc -platform Android-ARM -C Android-ARM .

I've been doing this on OSX with JDK 1.7.0_79 and using Adobe AIR 21 and Adobe AIR 19. I had the same issue with both of them. I also tried compiling with JDK 1.8.0_91 but still the same problem. JDK 1.6 is not viable because I need the Android features from newer SDKs.

Can somebody tell me what I might be doing wrong? Can somebody compile this source and use it? I'd be grateful for any help.