Adjust telemetry to DevTools protocol changes
We used to send trace events as stringized JSON within DevTools
protocol messages. We're changing them to be sent as raw objects,
sort of first-class DevTools protocol payload, which removes
the need for extra level of json de-serialization.
This adopts telemetry so it digest both old and new formats.
See also: https://codereview.chromium.org/
18474006/
BUG=
Review URL: https://chromiumcodereview.appspot.com/
19617003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@213433 0039d316-1c4b-4281-b951-d872f2087c98