Suppose the last committed URL in a RFH is "http://foo.com/", and the frame is now navigated to "http://foo.com/#ref", initiated from the browser side (e.g. by the user typing in the omnibox).

WebContentsObservers see the following:

  DidStartNavigation("http://foo.com/#ref", is_same_page=false, ...)
  DidStartNavigation("http://foo.com/#ref", is_same_page=true, ...)
  DidFinishNavigation("http://foo.com/#ref", is_same_page=true, ...)
  DidFinishNavigation("http://foo.com/#ref", is_same_page=false, ...)

While this scenario is probably rare, this sequence of events seems a bit confusing to observers.