ServiceWorker: Expose ServiceWorker interface to ServiceWorker

The ServiceWorker spec requires to expose it to ServiceWorker, but Blink
has exposed it only to Window:
https://w3c.github.io/ServiceWorker/#serviceworker-interface

Instances of the ServiceWorker interface have been available on
ServiceWorkerGlobalScope for a long time via |self.registration|, so this isn't
exposing anything new (see https://crbug.com/437677).

Ideally, this should also be exposed to DedicatedWorker and SharedWorker, but
this CL doesn't do it. This is because Blink hasn't supported ServiceWorker APIs
on the workers yet, and exposing the interface to the workers may churn feature
detections etc (see https://crbug.com/371690).

Bug: 999023
Change-Id: I5b36706d4d09dd830af00097bc9c724e3adf56b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775942
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692391}

third_party/blink/renderer/modules/service_worker/service_worker.idl

@@ -40,7 +40,11 @@ enum ServiceWorkerState {
 
 [
     ActiveScriptWrappable,
-    SecureContext
+    SecureContext,
+    // TODO(https://crbug.com/999023): Expose this to Worker (not only to
+    // ServiceWorker) after Service Worker APIs are supported on dedicated
+    // workers and shared workers.
+    Exposed=(Window,ServiceWorker)
 ] interface ServiceWorker : EventTarget {
 
     [CallWith=ScriptState, RaisesException] void postMessage(any message, sequence<object> transfer);

third_party/blink/web_tests/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt

@@ -1247,6 +1247,16 @@ interface SecurityPolicyViolationEvent : Event
     getter statusCode
     getter violatedDirective
     method constructor
+interface ServiceWorker : EventTarget
+    attribute @@toStringTag
+    getter onerror
+    getter onstatechange
+    getter scriptURL
+    getter state
+    method constructor
+    method postMessage
+    setter onerror
+    setter onstatechange
 interface ServiceWorkerGlobalScope : WorkerGlobalScope
     attribute @@toStringTag
     method constructor

third_party/blink/web_tests/virtual/stable/http/tests/serviceworker/webexposed/global-interface-listing-service-worker-expected.txt

@@ -1089,6 +1089,16 @@ interface SecurityPolicyViolationEvent : Event
     getter statusCode
     getter violatedDirective
     method constructor
+interface ServiceWorker : EventTarget
+    attribute @@toStringTag
+    getter onerror
+    getter onstatechange
+    getter scriptURL
+    getter state
+    method constructor
+    method postMessage
+    setter onerror
+    setter onstatechange
 interface ServiceWorkerGlobalScope : WorkerGlobalScope
     attribute @@toStringTag
     method constructor