To reproduce, run the system tests on a system running Windows 10 version 1803 with Hi-DPI scaling at 125%

$ gradle -PFULL_TEST=true :systemTests:test --tests InitialSizeTest

test.javafx.stage.InitialSizeTest > testInitialSize FAILED
    java.lang.AssertionError: Stage width expected:<100.0> but was:<132.8000030517578>
        at org.junit.Assert.fail(Assert.java:91)
        at org.junit.Assert.failNotEquals(Assert.java:645)
        at org.junit.Assert.assertEquals(Assert.java:441)
        at test.javafx.stage.InitialSizeTest.testInitialSize(InitialSizeTest.java:100)