When set jnlp.nativeMixedCodeDialog to false, applet that contains both signed and unsigned code will show a java mixed code dialog(java-mixedcode-dialog.png). But no such dialog for javafx apps that contains both signed and unsigned code.
 
ENV: win7/x64/jre8-b122
Steps to reproduce:
1) Set -Djnlp.nativeMixedCodeDialog=false to disable native mixedcode dialog:
Open JCP->Java->View, add -Djnlp.nativeMixedCodeDialog=false to Java Runtime Parameters For Applets
2) Set security level to medium
3) Disable OCSP/CRL check or make sure you can access to internet
4) Load javafx app that contains both signed and unsigned code from browser: http://sqeweb.us.oracle.com/net/sqenfs-1/export1/comp/jsn/users/crystal/DO_NOT_REMOVE_ME/jrebug/MixedCodeTestFX/html/MixedCodeApplet.html
5) An unsigned dialog will show up. Accept it
6) Another signed warning dialog will show up. Accept it
7) If the fx app gets loaded successfully directly without showing java mixed code dialog, then this issue is reproduced.

For applet, a java mixed code dialog will show up when setting jnlp.nativeMixedCodeDialog to false
1) Set -Djnlp.nativeMixedCodeDialog=false to disable native mixedcode dialog:
Open JCP->Java->View, add -Djnlp.nativeMixedCodeDialog=false to Java Runtime Parameters For Applets
2) Set security level to medium
3) Disable OCSP/CRL check or make sure you can access to internet
4) Load applet that contains both signed and unsigned code from browser: http://sqeweb.us.oracle.com/net/sqenfs-1/export1/comp/jsn/users/crystal/DO_NOT_REMOVE_ME/jrebug/mixedcodeJPI/html/testClickNoOnMixedCodeSigendToUnsigned.html
5) A security warning dialog will show up. Accept it
6) Another warning dialog will show up. Accept it
7) A java mixedcode dialog will show up. See attached java-mixedcode-dialog.png

With jnlp.nativeMixedCodeDialog=ture or just don't set jnlp.nativeMixedCodeDialog, both applet and javafx app will show native mixedcode dialog:
1) Set -Djnlp.nativeMixedCodeDialog=true
Open JCP->Java->View, add -Djnlp.nativeMixedCodeDialog=true to Java Runtime Parameters For Applets
2) Set security level to medium
3) Disable OCSP/CRL check or make sure you can access to internet
4) Load above applet or javafx app that contains both signed and unsigned code from browser
5) A security warning dialog will show up. Accept it
6) Another warning dialog will show up. Accept it
7) A native mixedcode dialog will show up. See attached native-mixedcode-dialog.png