Basic fetch flow

gistfile1.txt

Drastic simplification of the browser networking model.

API (<img>, <script>, XMLHttpRequest, fetch(), etc.)
  Creates a request with various settings
  Invokes Fetch with that request
  Uses the returned response in various ways.

Fetch (takes a request, returns a response)
  If scheme is not http/https, follow scheme-specific rules to create a response.
  If there's a service worker (and this invocation of Fetch did not come from a service worker), invoke Service worker.
  If that doesn't result in a response, use HTTP cache.
  If that doesn't result in a response, use network.
  Return response.
  
Service worker (takes a request, returns null or a response)
  Can do anything it likes to get to a response, including using an API such as `fetch()`.
  Return null or response.