Bug 1189685 - Part 1: Ensure that the state of all ServiceWorker instances is up to date when dispatching statechange events; r=bkelly

dom/workers/ServiceWorker.cpp

@@ -101,16 +101,6 @@ ServiceWorker::PostMessage(JSContext* aCx, JS::Handle<JS::Value> aMessage,
   aRv = workerPrivate->SendMessageEvent(aCx, aMessage, aTransferable, Move(clientInfo));
 }
 
-void
-ServiceWorker::QueueStateChangeEvent(ServiceWorkerState aState)
-{
-  nsCOMPtr<nsIRunnable> r =
-    NS_NewRunnableMethodWithArg<ServiceWorkerState>(this,
-                                                    &ServiceWorker::DispatchStateChange,
-                                                    aState);
-  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(NS_DispatchToMainThread(r)));
-}
-
 } // namespace workers
 } // namespace dom
 } // namespace mozilla

dom/workers/ServiceWorker.h

@@ -55,13 +55,9 @@ public:
   void
   DispatchStateChange(ServiceWorkerState aState)
   {
-    SetState(aState);
     DOMEventTargetHelper::DispatchTrustedEvent(NS_LITERAL_STRING("statechange"));
   }
 
-  void
-  QueueStateChangeEvent(ServiceWorkerState aState);
-
 #ifdef XP_WIN
 #undef PostMessage
 #endif

dom/workers/ServiceWorkerManager.cpp

@@ -4212,6 +4212,42 @@ ServiceWorkerInfo::RemoveWorker(ServiceWorker* aWorker)
   mInstances.RemoveElement(aWorker);
 }
 
+namespace {
+
+class ChangeStateUpdater final : public nsRunnable
+{
+public:
+  ChangeStateUpdater(const nsTArray<ServiceWorker*>& aInstances,
+                     ServiceWorkerState aState)
+    : mState(aState)
+  {
+    for (size_t i = 0; i < aInstances.Length(); ++i) {
+      mInstances.AppendElement(aInstances[i]);
+    }
+  }
+
+  NS_IMETHODIMP Run()
+  {
+    // We need to update the state of all instances atomically before notifying
+    // them to make sure that the observed state for all instances inside
+    // statechange event handlers is correct.
+    for (size_t i = 0; i < mInstances.Length(); ++i) {
+      mInstances[i]->SetState(mState);
+    }
+    for (size_t i = 0; i < mInstances.Length(); ++i) {
+      mInstances[i]->DispatchStateChange(mState);
+    }
+
+    return NS_OK;
+  }
+
+private:
+  nsAutoTArray<RefPtr<ServiceWorker>, 1> mInstances;
+  ServiceWorkerState mState;
+};
+
+}
+
 void
 ServiceWorkerInfo::UpdateState(ServiceWorkerState aState)
 {
@@ -4228,9 +4264,8 @@ ServiceWorkerInfo::UpdateState(ServiceWorkerState aState)
   MOZ_ASSERT_IF(mState == ServiceWorkerState::Activated, aState == ServiceWorkerState::Redundant);
 #endif
   mState = aState;
-  for (uint32_t i = 0; i < mInstances.Length(); ++i) {
-    mInstances[i]->QueueStateChangeEvent(mState);
-  }
+  nsCOMPtr<nsIRunnable> r = new ChangeStateUpdater(mInstances, mState);
+  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(NS_DispatchToMainThread(r.forget())));
 }
 
 ServiceWorkerInfo::ServiceWorkerInfo(ServiceWorkerRegistrationInfo* aReg,