Use task runner for DCHECK in ServiceWorkerGlobalScopeProxy

There were some DCHECK(IsMainThread()) in
ServiceWorkerGlobalScopeProxy. When we move service worker
startup off the main thread, these DCHECKs will start
failing. Use |parent_task_runner_| instead.

Bug: 692909
Change-Id: I92c788184b9b3753bf6eb2eec5393471e70e439e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1732669Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683485}

third_party/blink/renderer/modules/service_worker/service_worker_global_scope_proxy.cc

@@ -68,7 +68,7 @@ ServiceWorkerGlobalScopeProxy::Create(WebEmbeddedWorkerImpl& embedded_worker,
 }
 
 ServiceWorkerGlobalScopeProxy::~ServiceWorkerGlobalScopeProxy() {
-  DCHECK(IsMainThread());
+  DCHECK(parent_task_runner_->BelongsToCurrentThread());
   // Verify that the proxy has been detached.
   DCHECK(!embedded_worker_);
 }
@@ -312,19 +312,18 @@ ServiceWorkerGlobalScopeProxy::ServiceWorkerGlobalScopeProxy(
     : embedded_worker_(&embedded_worker),
       client_(&client),
       worker_global_scope_(nullptr) {
-  DCHECK(IsMainThread());
   DETACH_FROM_THREAD(worker_thread_checker_);
   parent_task_runner_ = Thread::Current()->GetTaskRunner();
 }
 
 void ServiceWorkerGlobalScopeProxy::Detach() {
-  DCHECK(IsMainThread());
+  DCHECK(parent_task_runner_->BelongsToCurrentThread());
   embedded_worker_ = nullptr;
   client_ = nullptr;
 }
 
 void ServiceWorkerGlobalScopeProxy::TerminateWorkerContext() {
-  DCHECK(IsMainThread());
+  DCHECK(parent_task_runner_->BelongsToCurrentThread());
   embedded_worker_->TerminateWorkerContext();
 }
 

third_party/blink/renderer/modules/service_worker/service_worker_global_scope_proxy.h

@@ -62,6 +62,9 @@ class WebServiceWorkerContextClient;
 // An instance of this class is supposed to outlive until
 // workerThreadTerminated() is called by its corresponding
 // WorkerGlobalScope.
+//
+// TODO(bashi): Update the above comment and method comments once we move
+// creation of this class off the main thread.
 class ServiceWorkerGlobalScopeProxy final : public WebServiceWorkerContextProxy,
                                             public WorkerReportingProxy {
  public: