Web Inspector: Exceptions in Network timeline when resource updates and filters are...

Web Inspector: Exceptions in Network timeline when resource updates and filters are applied
https://bugs.webkit.org/show_bug.cgi?id=146609

Reviewed by Joseph Pecoraro.

* UserInterface/Views/DataGrid.js:
(WebInspector.DataGrid.prototype.insertChild):
(WebInspector.DataGrid.prototype.removeChild):
(WebInspector.DataGridNode.prototype.savePosition):
Convert exceptions to asserts and early returns.

* UserInterface/Views/TimelineDataGrid.js:
(WebInspector.TimelineDataGrid.prototype._refreshDirtyDataGridNodes): Add some asserts and checks.

* UserInterface/Views/TreeOutline.js:
(WebInspector.TreeOutline.prototype.appendChild):
(WebInspector.TreeOutline.prototype.insertChild):
(WebInspector.TreeOutline.prototype.removeChildAtIndex):
(WebInspector.TreeOutline.prototype.removeChild):
Convert exceptions to asserts and early returns.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@186306 268f45cc-cd09-0410-ab3c-d52691b4dbfc