[whatwg] Ambiguity re firing the popstate event

[Justin Lebar]

Section 6.5.9.1 [1] says:

> The popstate event is fired when navigating to a session history entry that represents a state object.

In contrast, section 6.5.9 [2] indicates in step 10 that a popstate
event is fired if the history entry represents a state object or the
first entry for a document.

Unfortunately this ambiguity has caused WebKit and Mozilla to
implement popstate in two different ways [3].

I think we can resolve this in the spec by changing the line from 6.5.9.1 to:

> The popstate event is fired when navigating to a session history entry.

-Justin

[1] http://www.whatwg.org/specs/web-apps/current-work/multipage/history.html#event-definitions
[2] http://www.whatwg.org/specs/web-apps/current-work/multipage/history.html#history-traversal
[3] https://bugs.webkit.org/show_bug.cgi?id=41372