Web Inspector: HeapSnapshot: speed-up calculateObjectToWindowDistance

Web Inspector: HeapSnapshot: speed-up calculateObjectToWindowDistance
https://bugs.webkit.org/show_bug.cgi?id=86718

The idea is to switch from nodeIndex2distance array to nodeOrdinal2distance external array.
Due to nature of nodeIndex values the original array was sparsed.

Reviewed by Yury Semikhatsky.

* inspector/front-end/HeapSnapshot.js:
(WebInspector.HeapSnapshotNode.prototype.get distanceToWindow):
(WebInspector.HeapSnapshot.prototype._calculateObjectToWindowDistance):
(WebInspector.HeapSnapshot.prototype._bfs):
(WebInspector.HeapSnapshot.prototype._buildAggregates):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@117437 268f45cc-cd09-0410-ab3c-d52691b4dbfc