JavaFX WebView in plugin and ClassLoader

I'm trying to embed an JavaFX WebView into my plugin. (using oracle jre 8u181)

I found that the jfxrt.jar is loaded by com.intellij.util.lang.UrlClassLoader but not Launcher$ExtClassLoader (maybe this is intended), while in the handle of DataURLDecoder::decode, it would try to callback to JavaVM using callOnMainThread. The callOnMainThread would use WTF::scheduleDispatchFunctionsOnMainThread then AttachThreadToJavaEnv::AttachThreadToJavaEnv and eventually jvm->AttachCurrentThread to enter the java world (it is a new thread created in native code).

static JGClass jMainThreadCls(env->FindClass("com/sun/webkit/MainThread"));

static jmethodID mid = env->GetStaticMethodID(
        jMainThreadCls,
        "fwkScheduleDispatchFunctions",
        "()V");

Now the env->FindClass in the scheduleDispatchFunctionsOnMainThread would use java.lang.ClassLoader.getSystemClassLoader() which is Launcher$AppClassLoader but not com.intellij.util.lang.UrlClassLoader (MISMATCH!!)

So if you add some image using data protocol like <img src="data:image/png;base64,..."> would trigger this bug.

val mainPanel = JFXPanel()
val img = "iVBORw0KGgoAAAANSUhEUgAAAGQAAAAKCAYAAABCHPt+AAAAKUlEQVR42u3RAQ0AAAgDIG1u81vDTahAZyrFGS1ECEKEIEQIQoQg5LcF678Y92/zlF8AAAAASUVORK5CYII="
Platform.runLater {
    val webView = WebView("<img src=\"data:image/png;base64,$img\">")
    webView.engine.loadContent()
    myWebView = webView
    mainPanel.scene = Scene(webView)
}

this code could reproduce the bug, and you would see in console

internal base64
Exception in thread "Thread-64" java.lang.NullPointerException
at com.sun.webkit.MainThread.fwkScheduleDispatchFunctions(MainThread.java:34)