Forward original fragment identifier into System Preview

Forward original fragment identifier into System Preview
https://bugs.webkit.org/show_bug.cgi?id=191141
<rdar://problem/45717542>

Reviewed by Wenson Hsieh.

If the URL used by the page includes a fragment identifier, use
it when telling QuickLook to open a local file.

* UIProcess/Cocoa/DownloadClient.mm:
(WebKit::DownloadClient::didFinish): Append original fragment identifier
to the destination URL.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@237664 268f45cc-cd09-0410-ab3c-d52691b4dbfc