Crosswalk's XWalkView (an alternative to Webview) not working with AppBarLayout + CoordinatorLayout

Question

I'm trying to achieve the scrolling Toolbar technique (hiding Toolbar when scrolling down in a sibling child view) using CoordinatorLayout and AppBarLayout.

I'm using Crosswalk's XWalkView (it's a view which functions like WebView).

When using regular WebView (inside a NestedScrollView) I can achieve the wanted effect:

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_scrollFlags="scroll|enterAlways" />

    </android.support.design.widget.AppBarLayout>

    <android.support.v4.widget.NestedScrollView
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <WebView
            android:id="@+id/webViewOrig"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

    </android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>

However when using the XWalkView in the same way, I can't get it to work. After using the following XML layout:

<android.support.v4.widget.NestedScrollView
        android:id="@+id/scrollView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fillViewport = "true"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <org.xwalk.core.XWalkView
            android:id="@+id/webViewCross"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>
</android.support.v4.widget.NestedScrollView>

the view doesn't even appear.

When removing the following line

app:layout_behavior="@string/appbar_scrolling_view_behavior"

the XWalkView is at least displayed but on the whole screen and on top of the Toolbar.

What should I do to make it work? Since it's an open-source I should be able to make it work... I suspect it's either subclass XWalkView and implement some interface (NestedScrollingChild?) or creating a custom behaviour by subclassing CoordinatorLayout.Behavior or AppBarLayout.ScrollingViewBehavior.

Any ideas?

BTW XWalkView is using internally either SurfaceView or TextureView to render the web content.