Web Inspector: clicking "Show All Nodes" button throws TypeError
https://bugs.webkit.org/show_bug.cgi?id=133701

Reviewed by Timothy Hatcher.

The method used for isEventWithinDisclosureTriangle needs to consider the possibility that the
targeted TreeElement isn't contained within the visible DOM, for instance in the case of the
"Show All Nodes" button immediately after it is pressed.

* UserInterface/Views/TreeOutline.js:
(TreeElement.prototype.isEventWithinDisclosureTriangle): Check to make sure TreeElement node is in the visible DOM.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170416 268f45cc-cd09-0410-ab3c-d52691b4dbfc