service worker: Remove redundant OnStopped IPC when script fetch fails

We can remove the IPC from FailedTo{LoadClassic,FetchModule}Script()
because:
* After crrev.com/c/1819282 ServiceWorkerGlobalScope calls close()
  when top-level script fetch failed. Close() eventually invokes
  ServiceWorkerContextClient::WorkerContextDestroyed() which sends
  the IPC.
* The reason we sent OnStopped IPC from
  FailedTo{LoadClassic,FetchModule}Script() was to support
  on-the-main-thread script fetch. We no longer support it.

This CL also ensures that we have test coverage of the linked bug.
Following browsertests fail without crrev.com/c/1819282 when this CL
is landed.

* ServiceWorkerVersionBrowserTest.StartNotFound
* ServiceWorkerBlackBoxBrowserTest.Registration

Bug: 1005650
Change-Id: Ie61b633b213ca4e8646c009d2f5a0569c55820a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824727Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700054}

content/renderer/service_worker/service_worker_context_client.cc

@@ -203,11 +203,6 @@ void ServiceWorkerContextClient::FailedToLoadClassicScript() {
   DCHECK(worker_task_runner_->RunsTasksInCurrentSequence());
   TRACE_EVENT_NESTABLE_ASYNC_END1("ServiceWorker", "LOAD_SCRIPT", this,
                                   "Status", "FailedToLoadClassicScript");
-  // Cleanly send an OnStopped() message instead of just breaking the
-  // Mojo connection on termination, for consistency with the other
-  // startup failure paths.
-  instance_host_->OnStopped();
-
   // The caller is responsible for terminating the thread which
   // eventually destroys |this|.
 }
@@ -216,11 +211,6 @@ void ServiceWorkerContextClient::FailedToFetchModuleScript() {
   DCHECK(worker_task_runner_->RunsTasksInCurrentSequence());
   TRACE_EVENT_NESTABLE_ASYNC_END1("ServiceWorker", "LOAD_SCRIPT", this,
                                   "Status", "FailedToFetchModuleScript");
-  // Cleanly send an OnStopped() message instead of just breaking the
-  // Mojo connection on termination, for consistency with the other
-  // startup failure paths.
-  instance_host_->OnStopped();
-
   // The caller is responsible for terminating the thread which
   // eventually destroys |this|.
 }