In latest jdk 11 code, ran test 20 times in Windows 7 and Ubuntu 16.04 it doesn't fail.
Ran the test in MacMini 10.13.3 and it failed first time itself.

#Test Results (version 2)
#Mon May 14 10:24:30 IST 2018
#-----testdescription-----
$file=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.java
$root=/Users/arapte/Desktop/Jay/client/open/test/jdk
author=artem.ananiev\: area\=awt.eventdispatching
keywords=bug6304473 bug6727884 headful
library=../../regtesthelpers
modules=java.desktop
run=USER_SPECIFIED build Util\nUSER_SPECIFIED main HandleExceptionOnEDT\n
source=HandleExceptionOnEDT.java
title=Tests that an exception on EDT is handled with ThreadGroup.uncaughtException()

#-----environment-----

#-----testresult-----
description=file\:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.java
elapsed=13811 0\:00\:13.811
end=Mon May 14 10\:24\:30 IST 2018
environment=regtest
execStatus=Failed. Execution failed\: `main' threw exception\: java.lang.RuntimeException\: Test FAILED\: exception is not handled for modal dialog
harnessLoaderMode=Classpath Loader
harnessVariety=Full Bundle
hostname=fe80\:0\:0\:0\:2445\:8ff\:fe5b\:7460%8
javatestOS=Mac OS X 10.13.3 (x86_64)
javatestVersion=5.0
jtregVersion=jtreg 4.2 fcs b12
modules=java.desktop
script=com.sun.javatest.regtest.exec.RegressionScript
sections=script_messages build compile build compile main
start=Mon May 14 10\:24\:16 IST 2018
test=java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.java
testJDK=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home
totalTime=13837
user.name=arapte
work=/Users/arapte/Desktop/Jay/client/JTwork/java/awt/EventDispatchThread/HandleExceptionOnEDT

#section:script_messages
----------messages:(7/500)----------
JDK under test: /Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home
java version "11-internal" 2018-09-25
Java(TM) SE Runtime Environment 18.9 (build 11-internal+0-jdk11-client.204)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11-internal+0-jdk11-client.204, mixed mode)
Library ../../regtesthelpers; kind: packages
   source directory: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers
   class directory: /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers

#section:build
----------messages:(5/143)----------
command: build Util
reason: User specified action: run build Util
Library ../../regtesthelpers:
  compile: Util
elapsed time (seconds): 3.348
result: Passed. Build successful

#section:compile
----------messages:(5/253)----------
command: compile /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers/Util.java
reason: .class file out of date or does not exist
Additional options from @modules: --add-modules java.desktop
Mode: othervm
elapsed time (seconds): 3.345
----------configuration:(5/232)----------
javac compilation environment
  add modules: java.desktop
  source path: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers
  class path: /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers

----------rerun:(21/1630)*----------
cd /Users/arapte/Desktop/Jay/client/JTwork/scratch && \\
HOME=/Users/arapte \\
LC_CTYPE=UTF-8 \\
PATH=/bin:/usr/bin \\
    /Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home/bin/javac \\
        -J-Dtest.src=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT \\
        -J-Dtest.src.path=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers \\
        -J-Dtest.classes=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d \\
        -J-Dtest.class.path=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers \\
        -J-Dtest.vm.opts= \\
        -J-Dtest.tool.vm.opts= \\
        -J-Dtest.compiler.opts= \\
        -J-Dtest.java.opts= \\
        -J-Dtest.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -J-Dcompile.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -J-Dtest.timeout.factor=1.0 \\
        -J-Dtest.modules=java.desktop \\
        --add-modules java.desktop \\
        -d /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers \\
        -sourcepath /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers \\
        -classpath /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers/Util.java
----------System.out:(0/0)----------
----------System.err:(4/351)----------
Note: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers/Util.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers/Util.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
result: Passed. Compilation successful

#section:build
----------messages:(5/153)----------
command: build HandleExceptionOnEDT
reason: Named class compiled on demand
Test directory:
  compile: HandleExceptionOnEDT
elapsed time (seconds): 1.059
result: Passed. Build successful

#section:compile
----------messages:(5/295)----------
command: compile /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.java
reason: .class file out of date or does not exist
Additional options from @modules: --add-modules java.desktop
Mode: othervm
elapsed time (seconds): 1.058
----------configuration:(8/592)----------
javac compilation environment
  add modules: java.desktop
  source path: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT
               /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers
  class path: /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT
               /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d
               /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers

----------rerun:(21/2036)*----------
cd /Users/arapte/Desktop/Jay/client/JTwork/scratch && \\
HOME=/Users/arapte \\
LC_CTYPE=UTF-8 \\
PATH=/bin:/usr/bin \\
    /Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home/bin/javac \\
        -J-Dtest.src=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT \\
        -J-Dtest.src.path=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers \\
        -J-Dtest.classes=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d \\
        -J-Dtest.class.path=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers \\
        -J-Dtest.vm.opts= \\
        -J-Dtest.tool.vm.opts= \\
        -J-Dtest.compiler.opts= \\
        -J-Dtest.java.opts= \\
        -J-Dtest.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -J-Dcompile.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -J-Dtest.timeout.factor=1.0 \\
        -J-Dtest.modules=java.desktop \\
        --add-modules java.desktop \\
        -d /Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d \\
        -sourcepath /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers \\
        -classpath /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers /Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.java
----------System.out:(0/0)----------
----------System.err:(0/0)----------
result: Passed. Compilation successful

#section:main
----------messages:(5/202)----------
command: main HandleExceptionOnEDT
reason: User specified action: run main HandleExceptionOnEDT
Mode: othervm
Additional options from @modules: --add-modules java.desktop
elapsed time (seconds): 4.148
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(0/0)----------
----------System.err:(13/919)----------
java.lang.RuntimeException: Test FAILED: exception is not handled for modal dialog
at HandleExceptionOnEDT.main(HandleExceptionOnEDT.java:128)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:569)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:115)
at java.base/java.lang.Thread.run(Thread.java:832)

JavaTest Message: Test threw exception: java.lang.RuntimeException: Test FAILED: exception is not handled for modal dialog
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.RuntimeException: Test FAILED: exception is not handled for modal dialog
----------rerun:(20/1897)*----------
cd /Users/arapte/Desktop/Jay/client/JTwork/scratch && \\
HOME=/Users/arapte \\
LC_CTYPE=UTF-8 \\
PATH=/bin:/usr/bin \\
CLASSPATH=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers:/Users/arapte/Desktop/Jay/jtreg/lib/javatest.jar:/Users/arapte/Desktop/Jay/jtreg/lib/jtreg.jar \\
    /Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home/bin/java \\
        -Dtest.src=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT \\
        -Dtest.src.path=/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/EventDispatchThread/HandleExceptionOnEDT:/Users/arapte/Desktop/Jay/client/open/test/jdk/java/awt/regtesthelpers \\
        -Dtest.classes=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d \\
        -Dtest.class.path=/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d:/Users/arapte/Desktop/Jay/client/JTwork/classes/java/awt/regtesthelpers \\
        -Dtest.vm.opts= \\
        -Dtest.tool.vm.opts= \\
        -Dtest.compiler.opts= \\
        -Dtest.java.opts= \\
        -Dtest.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -Dcompile.jdk=/Users/arapte/Desktop/Jay/jdk-11.jdk/Contents/Home \\
        -Dtest.timeout.factor=1.0 \\
        -Dtest.modules=java.desktop \\
        --add-modules java.desktop \\
        com.sun.javatest.regtest.agent.MainWrapper /Users/arapte/Desktop/Jay/client/JTwork/java/awt/EventDispatchThread/HandleExceptionOnEDT/HandleExceptionOnEDT.d/main.0.jta
result: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Test FAILED: exception is not handled for modal dialog


test result: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Test FAILED: exception is not handled for modal dialog