I'm attaching two screenshots, one from jdk9 b40 and another from this PIT build based on the client state before b68. Fonts rendered in JEditorPane by the latter build look much darker than with b40 and even b66, so there may be a regression.
Then again, it may be intentional change: I don't like this rendering but don't ask me how it _should_ look.

Test in question is Swing_AllComponents/Automated/LAF_OrientationSuite/JEditorPaneHtmlTest2 -- I have more of the similar tests failing because of that. Unfortunately, the test is not exactly standalone, and I need some time to prepare a small example, if necessary.