1. Open Web Inspector/DevTools, switch to the Elements panel 2. Double-click and modify any DOM attribute value, hit Enter The element whose attribute has been modified disappears (turns into a white space). This issue can be fixed by removing "this._treeOutline.element.addStyleClass("hidden");" in Source/WebCore/inspector/front-end/ElementsTreeOutline.js's _updateModifiedNodes() (which hides the entire DOM tree before updating). So this looks like a WebCore rendering issue. Some of you guys may have dealt with similar issues recently (like display value update, https://bugs.webkit.org/show_bug.cgi?id=74976), hence CC'ing you.
Fixed by pfeldman about 2-3 months ago.