It seems that Chrome's behavior contrasts to specification. If I understood the specs correctly, defining "subtree" for an element means that changes to the subtree of that element (including the element itself) should be reported. However, when executing this piece of code, I get nothing.
var observer = new WebKitMutationObserver(function(e){console.log(e);})
observer.observe(document.body, {subtree:true, attributes:true});
document.body.appendChild(document.createElement('div'));
What am I missing?
The documentation is unclear, but subtree is ignored unless you also specify childList:true.
The same holds true for attributes and attributeFilter.