DevTools: Timeline: speed-up records processing.

It was awfully slow because we updated selection and calculated aggregates for every added record.
So the complexity was at least n^2.
I moved the _updateSearchHighlight call to _onRecordingStopped

BUG=

Review URL: https://codereview.chromium.org/703113003

git-svn-id: svn://svn.chromium.org/blink/trunk@184909 bbb929c8-8fbe-4397-9dbb-9b2b20218538