Worker: Clean up WebSharedWorkerImpl::TerminateWorkerThread()

In WebSharedWorkerImpl::TerminateWorkerThread(), following if-conditions

  (1) if (shadow_page_ && !shadow_page_->WasInitialized())
  (2) if (worker_thread_)

are mutually exclusive, so we don't have to check the both conditions.

Bug: 987850
Change-Id: Ibfac267d4ed684966853c606a09ab2fd8bb31e05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1734733Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683931}

third_party/blink/renderer/core/exported/web_shared_worker_impl.cc

@@ -96,7 +96,8 @@ void WebSharedWorkerImpl::TerminateWorkerThread() {
     return;
   asked_to_terminate_ = true;
   appcache_host_->Detach();
-  if (shadow_page_ && !shadow_page_->WasInitialized()) {
+
+  if (!worker_thread_) {
     client_->WorkerScriptLoadFailed();
     // The worker thread hasn't been started yet. Immediately notify the client
     // of worker termination.
@@ -104,11 +105,10 @@ void WebSharedWorkerImpl::TerminateWorkerThread() {
     // |this| is deleted at this point.
     return;
   }
-  if (worker_thread_) {
-    worker_thread_->Terminate();
-    DevToolsAgent::WorkerThreadTerminated(shadow_page_->GetDocument(),
-                                          worker_thread_.get());
-  }
+  worker_thread_->Terminate();
+  DevToolsAgent::WorkerThreadTerminated(shadow_page_->GetDocument(),
+                                        worker_thread_.get());
+  // DidTerminateWorkerThread() will be called asynchronously.
 }
 
 void WebSharedWorkerImpl::OnShadowPageInitialized() {
@@ -159,6 +159,7 @@ void WebSharedWorkerImpl::DidCloseWorkerGlobalScope() {
   DCHECK(IsMainThread());
   client_->WorkerContextClosed();
   TerminateWorkerThread();
+  // DidTerminateWorkerThread() will be called asynchronously.
 }
 
 void WebSharedWorkerImpl::DidTerminateWorkerThread() {

third_party/blink/renderer/core/exported/web_shared_worker_impl.h

@@ -71,7 +71,9 @@ class WebURL;
 // methods must be called from a worker thread. Such methods are suffixed with
 // *OnWorkerThread or have header comments.
 //
-// Owned by WebSharedWorkerClient.
+// Owned by WebSharedWorkerClient. Destroyed in TerminateWorkerThread() or
+// DidTerminateWorkerThread() via
+// WebSharedWorkerClient::WorkerContextDestroyed().
 class CORE_EXPORT WebSharedWorkerImpl final : public WebSharedWorker,
                                               public WorkerShadowPage::Client {
  public:
@@ -116,12 +118,13 @@ class CORE_EXPORT WebSharedWorkerImpl final : public WebSharedWorker,
   void DidFailToFetchClassicScript();
   void DidEvaluateClassicScript(bool success);
   void DidCloseWorkerGlobalScope();
+  // This synchronously destroys |this|.
   void DidTerminateWorkerThread();
 
  private:
   SharedWorkerThread* GetWorkerThread() { return worker_thread_.get(); }
 
-  // Shuts down the worker thread.
+  // Shuts down the worker thread. This may synchronously destroy |this|.
   void TerminateWorkerThread();
 
   void OnAppCacheSelected();