The attached test case demonstrates that changing the 'content' CSS property of an element does not replace its content with the specified content. Toggling the 'display' property to 'none' and back causes the new content to show. RenderStyle already has a contentDataEquivalent() method (used for pseudo elements), but RenderStyle::diff doesn't check it.
Created attachment 11720 [details] Test case
(In reply to comment #0) > RenderStyle::diff doesn't check it. Oops, make that Node::diff :-)
Created attachment 12180 [details] Compare content data when computing style diff
Created attachment 12182 [details] Now with extra parentheses for better readability!
Comment on attachment 12182 [details] Now with extra parentheses for better readability! r=me
Committed revision 18572.