Followup: controller

[noamr]

Once #1329 is merged, Fetching would return a "controller". To make use of that controller, the following action items need to be resolved:

• HTML: Use the controller in the HTML & other specs for aborting/terminating: Editorial: Use fetch controller when terminating/aborting xhr#346
• Fetch: Add finalize to the controller, to replace the current finalize and report timing. Call finalize and report timing automatically on end-of-body #1413
• HTML (& CSS?): Refactor callers of finalize and report timing to use the new fetch controller's finalize
• WPT: Add tests that emphasizes that a resource timing entry is per-fetch and not per-response