[Web Inspector] Fix Sort by Initiator functionality of Network Panel.
https://bugs.webkit.org/show_bug.cgi?id=109135.

Patch by Pan Deng <pan.deng@intel.com> on 2013-02-20
Reviewed by Pavel Feldman.

A refactor for request initiator types, and the sort by Initiator functionality
was changed to sort by url and line number that displayed in initiator cell.

No new tests.

* inspector/front-end/NetworkPanel.js:
(WebInspector.NetworkDataGridNode.prototype._refreshInitiatorCell): save initiator displayedURL and displayedLineNumber
(WebInspector.NetworkDataGridNode.InitiatorComparator):
* inspector/front-end/NetworkRequest.js:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143564 268f45cc-cd09-0410-ab3c-d52691b4dbfc