The DOM breakpoints are not sent unless there's a previous JS breakpoint set. That's because JSC::Debugger expects a call to incNumberOfBreakpoints when the client needs the runtime to capture debugging information. Otherwise there will be no call frames available when the DOM breakpoints are triggered.
Are you looking to add UI for DOM breakpoints?
I (In reply to comment #2)
> Are you looking to add UI for DOM breakpoints?
I don't have any plans on this yet.
I was working on https://bugs.webkit.org/show_bug.cgi?id=123516 when I've discovered this issue. I'm touching some of the Inspector instrumentation and I thought I need to add a test for this case too.
It took me a while to figure out why the protocol test was not working, so I've added this bug to track the issue.
I can confirm that DOM breakpoints are working without JS breakpoints.