DevTools: Speedup search by node id in heap snapshot

There's no need to perfrom the full sort to find out what would be
the node index in the sorted array.

Review URL: https://codereview.chromium.org/196793022

git-svn-id: svn://svn.chromium.org/blink/trunk@169244 bbb929c8-8fbe-4397-9dbb-9b2b20218538