Store derived properties of TracingModel.Event right on the Event

All external Maps from TimelineTraceEventBindings were inlined and corresponding values are now stored as properties of TracingModel.Event.

BUG=361045

Review URL: https://codereview.chromium.org/299313007

git-svn-id: svn://svn.chromium.org/blink/trunk@174848 bbb929c8-8fbe-4397-9dbb-9b2b20218538