Timeline: select, not just reveal, record found by search

R=eustas@chromium.org, eustas, pfeldman

We used to just "reveal", i.e. scroll to, expand if needed and highlight for 2s
records found by search. This gets confusing now, as we have a proper cursor that
does not move and record details are not updated. So instead of just revealing
records, let's select them.

Review URL: https://codereview.chromium.org/100793007

git-svn-id: svn://svn.chromium.org/blink/trunk@163862 bbb929c8-8fbe-4397-9dbb-9b2b20218538