While triaging JDK-8086098, found this issue.
Please find the attached test case [webViewSample.zip]. This is about communication between JavaFX and HTML inside WebView.
Steps to reproduce:
1. Run the CallingJavaFromJSTest.java
2. Click on any Button.

EXPECTED VERSUS ACTUAL BEHAVIOR :
Expected:
Java method "javaMethod()" should be called.
Actual:
Java method "javaMethod()" is not being called.

But when we click on hyperlink second time, java method is being called and then clicking buttons also works.
Please find JDK results:
================
windows 10
--------
8u40 : pass
8u121 : pass
9b01 : pass
9ea+88 : pass
9ea+140: pass
9ea+146: pass
9-ea+147 : fail
9-ea+148 : fail
9ea+150 : fail
9-ea+163 : fail

windows 7
--------
8u40 : pass
8u121 : pass
9-ea+153 : fail

ubuntu
--------
8 : pass
8u121 : fail
9-ea : fail