[Invalidation Tracking] Include DescendantInvalidationSet id in trace events

This CL adds DescendantInvalidationSet "id" field in
invalidation tracking trace events.
This id will be used to join ScheduleStyleInvalidation
events and StyleInvalidatorInvalidation events in devtools.

ScheduleStyleInvalidation events are to be added in a
separate CL: https://crrev.com/664033002

BUG=410701

Review URL: https://codereview.chromium.org/669033002

git-svn-id: svn://svn.chromium.org/blink/trunk@184213 bbb929c8-8fbe-4397-9dbb-9b2b20218538