DevTools: move events array from Timeline.stop response to Timeline.stopped

It is a change in protocol.json.
events was a hidden property in the Timeline.stop command result.
Now it is the hidden property in Timeline.stopped event.

BUG=394780
R=alph@chromium.org, yurys@chromium.org

Review URL: https://codereview.chromium.org/397813006

git-svn-id: svn://svn.chromium.org/blink/trunk@178670 bbb929c8-8fbe-4397-9dbb-9b2b20218538