Consider merging https://chromium.googlesource.com/chromium/blink/+/4cb65a17e49d135e7d0d4209eb557e98b2d7b097 Document::setBody previously would create a deep copy of the node if you moved it from a different document and didn't allow framesets. Document::body would incorrectly return <frameset> even if <body> came first. I also made setBody AttachLazily just like doing appendChild(body) would have done. Spec: http://www.whatwg.org/specs/web-apps/current-work/multipage/dom.html#dom-document-body
Fixed the getter via Bug 159488. Fixing the setter via Bug 159490.