WebKit clears the set of custom swipe views at the end of WebPageProxy::didChangeBackForwardList, *after* calling into the client. This means that if the client wants to setCustomSwipeViews in didChangeBackForwardList, it won't be respected. Since there's only one client of this SPI, let's just stop clearing the list of custom swipe views in WebKit and leave that totally up to the client.
<rdar://problem/17926507>
Created attachment 236072 [details] patch
http://trac.webkit.org/changeset/172307