Created attachment 226481 [details] test case (last table in the page) Web Inspector: Computed style incorrect for tables set to display: table-row-group We're trying to track down a data table heuristics bug in bug 129369, and although the styles for the last table in the test case are set to display: table-row-group, the computed styles still come out as display: table. There might be a CSS bug here too, but at the very least there is a Web Inspector bug in that the style rules inspector shows the table-row-group styles applied (no strikethrough) yet the computed styles panel shows something else. Screen shot also shows that JS and CSSOM indicate the display property is the expected value, not what the Web Inspector displays in computed styles.
Created attachment 226482 [details] screen shot
I think the Inspector is showing the right thing. WebCore is likely taking the table-row-group values and converting it to table since it is not in a table parent? Computed style is likely correct (what WebCore is doing) and the $0.style object just parrots back the data. But there is likely an Inspector UI bug where this is using table-row-group and not getting what we expect.
More info: Results differ based on where this uses quirks mode rendering. Add a doctype and you get the expected values. Based on that, I think you're right that computed style is showing the right thing, but the Inspector UI bug is that the Rules tab of the Styles Inspector does now indicate that the rules are being overridden by the quirksmode rendering.
s/now/not/
<rdar://problem/28228572>