Once NetworkService ships, CrossSiteDocumentResourceHandler can be removed.


The following tests can be removed after CrossSiteDocumentResourceHandler is removed:

- CrossSiteDocumentBlockingServiceWorkerTest.NoNetwork
  (this test doesn't add value in the NetworkService world, where AFAIK ServiceWorker responses go straight to the right renderer process, without being seen by the browser process and/or the network process;  also note that CrossSiteDocumentBlockingServiceWorkerTest.NetworkToServiceWorkerResponse is still valuable because the responses tested there should still be going through the network service process)

- CrossSiteDocumentBlockingIsolatedOriginTest.BlockDocumentsFromIsolatedOrigin
  (hopefully by the time NetworkService ships, SitePerProcess would have already shipped and IsolateOrigins will no longer be a thing)


The following tests should be preserved, even after removing CrossSiteDocumentResourceHandler:

- All other browser tests in content/browser/loader/cross_site_document_blocking_browsertest.cc
  (with NetworkService it should be possible to simplify the code and unconditionally ignore some UMAs in InspectHistograms)

- All of content/browser/loader/cross_site_document_resource_handler_unittest.cc
  (this might be a bit tricky since these tests are somewhat closely-coupled with CrossSiteDocumentResourceHandler,
  but hopefully they can be moved to services/network/cross_origin_read_blocking_unittest.cc and tweaked to directly test CrossOriginReadBlocking::ResponseAnalyzer without loosing too much test coverage)