[ServiceWorker] ServiceWorkerContextObserverSynchronous::OnStartWorkerMessageSent

This method allows the extensions layer to get a notice that the
message to start a worker (`OnStartWorkerMessageSent`) has been sent.

This is needed to deterministically trigger a race condition with
`ResetURLLoaderFactories` in browsertests.

Design doc: http://go/defer-reset-url-loader-factories

Bug: 394523691
Change-Id: Ie43471f86d26c5c5478211bc0d82176b678b839a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6433846
Reviewed-by: Yoshisato Yanagisawa <yyanagisawa@chromium.org>
Commit-Queue: Andrea Orru <andreaorru@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1443867}

content/browser/service_worker/service_worker_context_core.cc

@@ -1229,6 +1229,16 @@ void ServiceWorkerContextCore::OnControlleeNavigationCommitted(
       version->version_id(), client_uuid, render_frame_host_id);
 }
 
+void ServiceWorkerContextCore::OnStartWorkerMessageSent(
+    ServiceWorkerVersion* version) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK_EQ(this, version->context().get());
+
+  for (auto& observer : sync_observer_list_->observers) {
+    observer.OnStartWorkerMessageSent(version->version_id(), version->scope());
+  }
+}
+
 void ServiceWorkerContextCore::OnRunningStateChanged(
     ServiceWorkerVersion* version) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);

content/browser/service_worker/service_worker_context_core.h

@@ -367,6 +367,7 @@ class CONTENT_EXPORT ServiceWorkerContextCore
   void OnNoControllees(ServiceWorkerVersion* version);
 
   // ServiceWorkerVersion::Observer overrides.
+  void OnStartWorkerMessageSent(ServiceWorkerVersion* version) override;
   void OnRunningStateChanged(ServiceWorkerVersion* version) override;
   void OnVersionStateChanged(ServiceWorkerVersion* version) override;
   void OnDevToolsRoutingIdChanged(ServiceWorkerVersion* version) override;

content/browser/service_worker/service_worker_version.cc

@@ -1463,6 +1463,12 @@ void ServiceWorkerVersion::OnStarting() {
   }
 }
 
+void ServiceWorkerVersion::OnStartWorkerMessageSent() {
+  for (auto& observer : observers_) {
+    observer.OnStartWorkerMessageSent(this);
+  }
+}
+
 void ServiceWorkerVersion::OnStarted(
     blink::mojom::ServiceWorkerStartStatus start_status,
     FetchHandlerType new_fetch_handler_type,

content/browser/service_worker/service_worker_version.h

@@ -180,6 +180,7 @@ class CONTENT_EXPORT ServiceWorkerVersion
 
   class Observer {
    public:
+    virtual void OnStartWorkerMessageSent(ServiceWorkerVersion* version) {}
     virtual void OnRunningStateChanged(ServiceWorkerVersion* version) {}
     virtual void OnVersionStateChanged(ServiceWorkerVersion* version) {}
     virtual void OnDevToolsRoutingIdChanged(ServiceWorkerVersion* version) {}
@@ -892,6 +893,7 @@ class CONTENT_EXPORT ServiceWorkerVersion
   void OnScriptLoaded() override;
   void OnProcessAllocated() override;
   void OnStarting() override;
+  void OnStartWorkerMessageSent() override;
   void OnStarted(blink::mojom::ServiceWorkerStartStatus status,
                  FetchHandlerType new_fetch_handler_type,
                  bool new_has_hid_event_handlers,

content/public/browser/service_worker_context.h

@@ -93,6 +93,9 @@ using ServiceWorkerScriptExecutionCallback =
 // synchronously with changes in //content.
 class ServiceWorkerContextObserverSynchronous : public base::CheckedObserver {
  public:
+  // Called after the message to start the service worker has been sent.
+  virtual void OnStartWorkerMessageSent(int64_t version_id, const GURL& scope) {
+  }
   // Called when the service worker with id `version_id` will be stopped.
   virtual void OnStopping(int64_t version_id,
                           const ServiceWorkerRunningInfo& worker_info) {}