DevTools: fix missing samples in CPU profile after r172795

Nodes parents must be calculated before the call to _fixMissingSamples.
The patch reverts one line change introduced by r172795.

TBR=yurys

Review URL: https://codereview.chromium.org/259093006

git-svn-id: svn://svn.chromium.org/blink/trunk@172860 bbb929c8-8fbe-4397-9dbb-9b2b20218538