[DevTools] Timeline: reveal all matching nodes when filtering.

Currently when user searches for sometinhg, he can traverse all matching nodes.
But when user filters, matching nodes inside (collapsed) nodes do not appear.

This patch reveals all matching nodes. Parents of matching nodes are shown, even
if they do not match themselves. User still can collapse branches he is not
interested in. When search query is changed, user collapsed nodes will be
expanded again.

Review URL: https://chromiumcodereview.appspot.com/19381002

git-svn-id: svn://svn.chromium.org/blink/trunk@156913 bbb929c8-8fbe-4397-9dbb-9b2b20218538